The Rabbit Test

After the discovery of hormones in the early 20th century, new methods of pregnancy testing were developed. Some of these involved animal use, but how did the rabbit test work, and when did it get replaced?

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Episode Transcript

Speaker 1 (00:01):
Welcome to Stuff you missed in History Class from how
Stuff Works dot com. Hello, and welcome to the podcast.
I'm Holly Frying and I'm Tracy d Wilson. So Tracy.
This weekend, I was hanging out in another city with
some friends. UM, and I made a joke referencing the

(00:24):
movie The Rabbit Test. Do you know that movie? I
know of it, but I don't think I've ever seen it.
I will tell you a funny story after I tell
you what the movie is about, because it evidences the
mind of a child and how they process information. So
in that movie, which is a comedy directed by the
late great Joan Rivers, Billy Crystal stars as a man
who gets pregnant and the title is a joke based

(00:46):
on the now outdated practice of using rabbits as part
of a medical test to determine if a woman was pregnant. Now,
this movie came out, like I said, in seventy eight.
So I was seven when it huh out, And I remember, Um,
I had said something like I don't know if I
had seen a poster or an ad or something, and
I was like rabbits, Like I was excited to see
this movie and my siblings, who are all a good

(01:09):
bit older than me. We're like, oh, no, that movie
is not for you, because of course it was about
sex and reproduction. But my perception as a seven year
old was that it must be a terrifying horror movies.
I didn't know until I was in my twenties and
it was a comedy. I was like, no, it's like
a scary sci fi thriller, is what I made up
in my head. Well, and and based on everything I

(01:31):
know of you, Holly, I was genuinely astonished when I
got this email from you with this outline last night,
because it contains a number of things that are just
not your bag, right, like talking about you know, pregnancy
and um um, and I'm going to get to the
animal testing things and we have a we have our
our our opt out discussion in a moment. But my

(01:56):
point in all of this is that I had had
mentioned this movie to friends, and those friends are all
a bit younger than my husband and I are, and
they had never heard of the movie, and they had
never heard of the use of rabbits in pregnancy testing.
And I was trying to explain this to them with
my not scientific knowledge and their eyes got really big
and they seemed completely incredulous and thought maybe I was

(02:19):
pulling one over on them. So, um, I was like, well,
I know what I want to work on next, and
it's this Because I thought everybody knew, they don't. Uh.
If you also listen to the podcast saw Bones and
you should, they indicated an episode on the history of
pregnancy testing, and it mentions the rabbit test very briefly,
but it's really more of a broad overview of how

(02:40):
pregnancy testing has evolved over the centuries, and we are
instead going to look really closely at how this particular
test and one very like it both were developed in
the twentieth century. So you may have surmised already, but
heads up, this episode is going to involve a significant
amount of discussion of animals being used in medical testing,
with an outcome of mortality for the animal in most cases. Um,

(03:04):
So if that is something that you would rather not
hear about or rather not perhaps share with younger history buffs,
you can tap right out of this one. Yeah. Yeah,
I still have a whole layer of surprise of like, well,
I love science, I know you do. It just seems
like you know you're talking about the movie coming across
as a terrifying horror movie. I feel like the subject

(03:25):
is like a holly terrifying horror movie. Yeah. No, I
mean it's not me. It's not me having a child,
and it doesn't really talk about like any of the
actual pregnancy, just the pathology and medical testing. So I
think that's why it's a little easier for me to
dig in on. And somehow I don't know why I

(03:48):
seem to be able to handle this particular discussion of
animal testing. Yeah, we'll see. I could start crying halfway through.
We'll see how it goes. It's always different typing it
than it is saying it. But definitely one of those
subjects that is always on, like the right of first
refusal list what I'm thinking of things to talk about. So,

(04:08):
uh today, Home pregnancy tests they're inexpensive, very common. Usually
the first way people find out if they are pregnant
just go to the store and pick one up. But
there have been plenty of folk medicine tests that people
could try on their own over the years before they
were actual working pregnancy tests and for a scientific confirmation

(04:29):
of that pregnancy. Up until the seventies, you pretty much
had to go to the doctor. You couldn't just pick
up a home test. The use of urine to test
for pregnancy was nothing new at all. It had been
part of how people tested for pregnancy for centuries. Yeah,
people had intuited that there was something going on with
urine where uh it was a way to determine if

(04:51):
someone was in fact carrying a child, But they were
not necessarily rooted in science. Always they involved things like,
you know, peeing on grain and see if it turned color.
But a really major development took place in nineteen o
two when E. H. Starling, who was a physician, and W. M. Bayliss,
who was a physiologist, discovered secreton. And secreton is a

(05:16):
polypeptide that is made up of more than two dozen
amino acids. But what is really important is that it
was the first hormone ever discovered. Secreton is a digestive hormone.
It has nothing to do specifically with reproduction and Starling
didn't start using the word hormone for several years. He
first introduced it into medical nomenclature and a lecture that

(05:38):
he gave at London's Royal College of Physicians in nineteen
o five titled on the Chemical Correlation of the Functions
of the Body, and in that lecture, Starling defined hormones
as quote the chemical messengers which, speeding from cell to
sell along the bloodstream, may coordinate the activities and growth
of different parts of the body. And from the point

(06:00):
where he established the term, all manner of discovery and
research in the field of hormones began. Yeah, and that's
still the pretty basic definition that you learn of what
a hormone is in school. Yeah, at a very basic level.
So from the nineteen teens, a number of researchers were
examining the link between hormones and pregnancy. Through the introduction

(06:22):
of extracts of human placenta into other animals in a
variety of laboratory experience, it became clear that there were
hormones in the mix that were related to reproduction. All
of this sounds so obvious now, but at the time,
I know, I think about like the shorthand of how
people just attribute like people's urge to uh, you know,

(06:44):
have romantic involvement with one another, they'll just go hormones.
But like at the time, this was like mind blowing
concept that that was what was driving your romantic interest. Yeah,
And the hormone that was eventually identified in all of
this was human choreonic gonadotropin, which is more commonly known
as hCG, and that was the hormone that unlocked the

(07:04):
door to pregnancy testing. So just for a little bit
of clarity, but not too much, because I'm not going
to give you the hard science because I will miss
something up. But hCG is actually four independent molecules which
each have their own functions in which are produced by
separate cells. hCG is not only used as an indicator
of pregnancy. Certain cancers can also be detected based on

(07:26):
tests which analyze hc G content in a person's bloodstream.
And hCG is present in women even when they are
not pregnant, although it's a pretty small amount. They don't
produce significant amounts unless they are crying a child. But
pregnancy tests are designed to measure the levels of hCG
and once that passes a certain threshold, it is a

(07:47):
reliable indicator of pregnancy. In six two German doctors Selma
Asheim and Bernhard Zondeck developed a pregnancy test that used mice.
The preparation was described in a nine team thirty article
in the journal California and Western Medicine by authors Herbert M. Evans,
m d. And Miriam E. Simpson, m D. As follows

(08:10):
the morning urine is sent into the laboratory and clean bottles.
They meaning Ashaim and Zondeck recommend the addition of one
drop of tri cresal per twenty five cubic centimeters of
urine if it is necessary for the sample to be
sent by mail. A group of five mice each wing
six to eight grahams is used to test each urine specimen.

(08:31):
So the mortality rate for mice just to test a
single person sample was quite high at that point, but
per Evans and Simpson, this test was far more reliable
than any other options, and it produced results in as
few as four days. It worked because the urine sample,
which was injected into very young mice in a specified regiment.

(08:52):
It was multiple injections over the course of several days
would catalyze sexual maturation in the mice if the urine
was from a pregnant woman. On the fifth day, between
ninety six hundred hours after the start of the injection process,
the mice were killed and then the crop seed based
on an examination of the mice's ovaries, doctor could determine
if the woman who had given the urine sample was pregnant.

(09:15):
If the ovaries remained mostly small and smooth, the test
was negative, but if there was enlargement and maturation beyond
the normal development, it was positive. Ash I'man's on Deck
also developed a variation on this test for cases where
someone might more urgently need to know if they were pregnant.
Although it came at a cost of more mice, They

(09:35):
used more mice in the experiment and then that they
dissected them earlier in the range past when they had
begun the testing. That larger sample set made up for
the shorter testing period. We are about to talk about
a little variation on the method that they developed, but
first we'll pause and have a quick word from one
of the sponsors that keeps the show going. Other doctors

(10:05):
took the work of the German team and the Asheim
Zondeck test, which was often abbreviated to just called be
called the AZ test, and they made slight tweaks to
the method for what worked best for their laboratory situation
and their staff at the University of California at Berkeley
in the late nineteen twenties, researchers opted to use six
rats for the procedure rather than mice, and they stored

(10:26):
the urine samples at freezing temperature before injection. They of
course heated it back up so that the animals were
not going to shock after the injection. Using rats was
actually more cost intensive than mice, but you see, Berkeley
had already had an established rat colony for use in
their laps. The primary benefit and using rats instead of
mice was the fact that all of the rats usually

(10:49):
survived the test at least the injection and sort of
incubation portion of the test, but in mouse based testing,
fift of the rodents died before they reached that day
five exam a nation stage, and both tests the error
rate was quite small, between one and two percent, and
according to data collected in Ashiman Zondex lab, this test

(11:09):
was also quite good at early detection. There were recorded
instances of positive results before any other clinical signs of
pregnancy were present, for example, just three to four days
after the patient had missed a menstrual period. Results were
most reliable though in cases of normal pregnancy, so in
instances of more problematic situations like a tubal pregnancy. The

(11:32):
results were, according to the German doctor's data, slightly less accurate.
This was at a time in medical science when diagnostic
tests weren't always common practice in Western medicine, and they
certainly weren't common specifically for women. Additionally, a lot of
doctors felt as though it was extraneous. They trusted their
experience and diagnostic abilities to determine if someone was pregnant

(11:53):
or not. There was concerned that testing labs removed for
the relationship and the trust between the doctor and the patient. Yeah,
this was particularly a problem UM in Great Britain. I
was reading one article that UM mentioned that this one
particular lab in Edinburgh had started taking mail in samples
and people were like, but they're bypassing their doctors just

(12:14):
to do a direct thing. Um. There were a lot
of a lot of concerns. And this is at a
point where there was insurance in Great Britain, but it
didn't always cover women, and it certainly didn't cover them
just wanting to find out if they were pregnant. That
was usually only for like an emergency, which we'll talk about. Additionally,
most of the time most women suspected they were pregnant

(12:35):
already and they went to their doctor just to confirm
what they already thought. And family practitioners used this as
evidence that there was not a real need for such
tests to become mainstream. In most cases, unless there was
an urgent medical dean to know if a woman was pregnant.
Health organizations and insurance companies where they existed, because insurance

(12:55):
didn't really start until the late nineteen twenties, were unlikely
to approve coverage for the cost of the test. Testing
samples sent through the mail was particularly looked down upon
us we just sort of alluded to. It was referred
to as postal pathology. That's a a criticism that still
exists today with all the various things that you can

(13:16):
test at home and kind of mail away. But this
test was recognized for its efficacy and it became more
and more commonly administered. Both Selmer Asheim and Bernard Zondeck
were Jewish, and both of them chose to leave Germany.
I say chose, but they really had to for their
lives in nineteen thirty three as the Nazi Party came
into power, and they left their lab behind in the process.

(13:38):
In thirty one, the landscape for pregnancy testing shifted when
a similar test to the A Z test was introduced
at the University of Pennsylvania by Maurice Harold Friedman and
Maxwell Edward Lapham. Freedman, who was born on October three
and Gary, Indiana, had been with the University of Pennsylvania
as a faculty member since he had earned his bachelor's

(14:00):
degree PhD and m d at the University of Chicago
starting in nineteen nine, so he went into his undergrad
at just sixteen, so he was still quite young when
he developed the rabbit test, and Maxwell E. Lapham, who
was born in newfe New York, was just three years
older than his collaborator, and he was working at the
university hospital at the time. And an article titled a

(14:21):
Simple Rapid Procedure for the Laboratory Diagnosis of Early Pregnancies
in the March issue of the American Journal of Obstetrics
and Gynecology, Friedman and Lapham wrote about their choice to
move away from mice for their test, starting with a
reference to the as test, It said quote Yet this
test admirable, though it is has some distinct disadvantages, one

(14:44):
of which may make it impractical in a laboratory or
hospital not closely affiliated with some university or institute. To
perform the zondek Asheim test, it's essential to be in
in a position to command a ready supply of amateur
mice weighing from sixt grahams. If a large breeding colony
of mice is not easily available, some difficulty might be

(15:05):
encountered in procuring suitable animals at a time as test
as desired. Moreover, even if one had at hand enough
of the immature mice to answer the calculated requirements for
a given week, and for some reason or other the
number of samples submitted fell below expectations, the unused animals
would soon mature beyond their usefulness, so that another group

(15:27):
of the immature animals would have to be gotten. Freedman
and Lapham's test used rabbits instead of mice, and just
as rats were more of a burden to support than mice,
rabbits took a lot more effort and resources to keep
in a lab setting. But there were some very significant
benefits to rabbits over mice. For one, it required only
one to two specimens rather than six. Aside from just

(15:50):
the number of creatures harmed. This also just meant one
or two necropsies rather than half a dozen, and unlike mice,
rabbits only ovulate after mating. That meant they didn't need
to use only very young animals. With mice, the very
young specimens were used to avoid any confusion that might
arise should Amounse just be developing a natural estrous cycle,

(16:11):
which would look pretty similar to a positive result in
the testing. As long as they knew the rabbit's history
and it had been isolated because exposure to other female
rabbits could cause estrus, it could stay viable as a
test subject until it was needed, instead of aging out
of usefulness for testing purposes. But even if a rabbit
had not been fully isolated, it could still potentially be

(16:34):
used per Friedman and Lapham quote. In case one has
not had opportunity to isolate the rabbits for the desired period,
and it is found necessary to perform a test, it
is safe to use a rabbit that has been isolated
in the laboratory for only eight or ten days, even
if the rabbit in question had had coitus just before
it was obtained. The corporal lutilla of pregnancy or pseudo

(16:58):
pregnancy would then be least eight or ten days old
and could not be confused with the fresh corporate lutia
or corporal hemorrhagica produced by the injections of an active urine. Briefly,
then one may safely use all rabbits that are not
demonstrably pregnant at the end of three weeks of isolation.
Pathologists also found the rabbits easier to handle, and it

(17:19):
was easier to administer injections into the veins of their ears.
They could perform the necropsy without the need for a
microscope or a magnifying glass because the results were observable
to the naked eye rather than needing to be magnified. Yeah,
that was not the case with mice or you had
to look very closely at their tiny, tiny organs. You
could literally just do the necropcy and go yep, this

(17:40):
one is positive. But the big, big difference was that
a rabbit test could be turned around in forty eight
hours rather than five days. While Lapham and Friedman tried
a similar method of earlier necropsy that had been used
in mice, as you remember, they had just up the
number of mice used and then did a test doing
sort of pattern recognition at a shorter interval. They actually

(18:02):
found the results a lot less reliable when they try
a similar method in rabbits. We're about to get into
the numbers involved in the research that Freedman and Lapham
used to test their rabbit method, but first we will
take a quick sponsor break. To test their approach, the

(18:25):
University of Pennsylvania team used a hundred and eleven samples.
Three samples were deemed too toxic to use in the test,
and the specific nature of the toxicity is not described
in the Freedman and lap of paper, but a lab
in Edinburgh, Scotland, which did quite a lot of pregnancy
testing in the nineteen thirties, described sometimes getting samples of

(18:45):
urine which were green because the women who had given
them had used some sort of chemical means to try
to avoid pregnancy. Those samples were lethal to mice, which
was the testing animal that the Edinburgh lab used, so
the test would not work. Freedman and Lapa mentioned as
a desire to find a way to handle so called
toxic samples. Writing quote zon Deck reports that about six

(19:07):
percent of the samples submitted were too toxic. To be handled,
and to obviate this difficulty, he has devised a method
by which these toxic urines may be made innocuous. Since
the appearance of this paper, we have not encountered a
sample with which to test this procedure, so that left
a hundred and eight samples for the study, and twenty
five of those samples were from women who were in

(19:29):
their last months of gestation, and all of their samples,
as expected, yielded positive test results. Thirty two of the
samples were from women who had gone to the clinic
at the university hospital to determine if they were pregnant.
Twenty five of them tested positive for pregnancy, and the
research team was able to track twenty two of those
women to further verify that they had been pregnant, although

(19:51):
not all of them carried those pregnancies to full term.
The remaining three did not remain in contact with the study.
There were fifty one negative test results from this viable
group of a hundred eight samples. Two of those samples
were from men and were from women in the hospital
who were known to have been not pregnant at the
time of testing, including several with conditions that might clinically

(20:13):
present as looking pregnant without a test, like they had
nausea or their abdomens were swollen, something like that. Yes,
so they wanted to include people that they absolutely knew
were not pregnant to prove that the tests was accurate
in both positive and negative and also people who might
be told by a doctor who was just examining them

(20:34):
that they were probably pregnant but were in fact not.
Twenty four of the negative test results had been for
women who had visited the clinic to determine if they
were pregnant, and the study remained in contact with eighteen
of those patients and they were verified as non pregnant.
That left ninety two cases for which the doctors felt
they had adequate data for the inclusion in the study
statistical analysis, and that left them with an error rate

(20:57):
of zero. But in their paper Forman and Lapham wrote,
it is likely that if we had more material, we
might have encountered an error or two. Yeah, they were
not asserting that it was a percent effect of all
the time, um, but of the ninety two that had
been that it had been paired down to after they
uh had to leave out the toxic urine samples and

(21:19):
the ones that they lost track of it was accurate
in that data. The Freedman Lapham test was adopted more
readily than its predecessor, the mouse version, in part because
the asy test had blazed a trail already, so people
already had this idea that this test was worthwhile and
was accurate, and also for all of the reasons that

(21:40):
were laid out in the paper published by Freedman and Lapham.
For example, hospitals found it much easier to set up
a lab for a smaller number of rabbits than huge
numbers of mice, which they would have to continually be
breeding to get workable um animals that they could use
in testing, even though it was still more expensive to
house a rabbit, and the reliability and the speedier assessment

(22:02):
during necropsy made this test much more appealing as well.
And as a bit of myth busting, you may have
heard the joke the rabbit died as a shorthand way
to say that somebody is pregnant, and this has been
a long a longstanding misconception connected to this test. I
think both Holly and I at some point have probably
said that I know I have repeated that myth, So

(22:23):
apologies to anyone that heard that from my lips. You
got misinformation. Yeah, the positive test result was not indicated
by the rabbit dying. The rabbits had to be euthanized
and necrop seed. The positive test result was definitely not
the cause of the death. Correct. And while the rabbit
test was more popular than the mouse test that preceded it,

(22:46):
there was another way to test for pregnancy that followed
in the nineteen thirties, so not very long after the
rabbit test was introduced, called the frog test, and this
one introduced into Western medicine by British biologist Lancelot hogban
didn't kill the test animal, Xenopus levis. Frogs used in
this test would begin ovulating and dropping eggs quite quickly

(23:07):
after being injected with urine that contained hCG in the
levels consistent with pregnancy. You will also sometimes hear this
referred to as the Buffo test. That species was originally
named Buffo levis before the name changed to Xenopus. So
these frogs displayed their results in mere hours compared to
the days that it took with previous methods of mice

(23:28):
and rabbits, and the same frog could be used for
repeated testing since there wasn't a necropsy needed to confirm
these results. Yeah, this is also one of those things
that has possibly led to some species integration in places
it is not natural for it to exist, because it appears,
at least based on what I read, that this really

(23:48):
caused no harm to the frogs whatsoever. And so these
labs would end up with lots and lots of frogs
and eventually they would start letting some go. So they
had originated in South Africa and then ended up up
being let loose outside of labs throughout the Western world.
We've done, uh like invasive species have come up on

(24:09):
the show before, but I don't think I have ever
heard of invasive pregnancy test frogs and the invasive frogs
that have have gone on to retire from being pregnancy
tests ers. They also eventually realized that they could use
male frogs as well, and they would basically release sperm,
and they actually had a much faster test result than
the female frogs, So both both males and females of

(24:33):
the species ended up being used. But hogg Ban did
not get to retain a clear claim to this discovery.
While he had apparently suggested that these frogs could be
used to detect certain hormones and pregnant women. He didn't
really land at the idea that the frogs could be
used to design a pregnancy test, and he did not
set up any of the testing around it. It was

(24:54):
Hogben's student Hill L. Shapiro and Shapiro's research partner, Harry's
Warrenstein who act took the idea from theoretical to practical
by designing executing studies with the frogs. Of course, the
frog test caught on because if its benefits over the
other options, and it was used until the nineteen sixties,
when pregnancy tests were developed that didn't involve the use

(25:15):
of animals at all. After that, home kits eventually hit
the market in the nineteen seventies, the first of which
was called Predictor and which took two hours to offer
a result. These were a lot more convoluted than today's
where you just pe honest stick. If you have watched
the Netflix series Glow, you've seen what one looks like. Yeah, yeah,

(25:37):
And I should say that they there were other tests
being developed that did not involve animals before the nineteen sixties,
but they just you know, had not reached a level
of reliability that they could supplant these animal based testing options.
And as for the developers of the rabbit test, Maxwell E.
Lapham wrote a book titled Maternity Care in Rural Communities
in ninety eight, so later in that same decade after

(25:58):
they introduced the rabbit test. The year before that, he
had joined the faculty at Tulane University School of Medicine,
and he actually stayed with Tulane until the end of
his career. When he died at the age of eighty three,
it was in Tulane University Hospital and per his New
York Times obituary, during his time as dean of the
medical school, he had significantly bolstered the financing of the

(26:19):
school's research program, taking it from thirty thousand dollars to
five point five million, and that was basically just through
grant money. Maurice Freedman moved to the Washington, d c.
Area and worked for the Beltsville Agricultural Research Center. He
served in the Army Air Force in World War Two
as a medical officer and opened a private practice after
the war was over, specializing in internal medicine. He died

(26:41):
of cancer in nine at the age of eighty seven,
and one of Dr Friedman's more famous quotes regarding the
rabbit test was quote, it's highly reliable. The only more
reliable test is to wait nine months. That seems like
a fun place to end it, uh, since it is
a little bit to me, it's very fascinating, but you know,
it does get into animal testing, which is not the

(27:02):
most delightful topic, but it's an important part, I feel
like of our scientific um history, particularly as it relates
obviously to reproductive medicine, and it's something that people maybe
don't realize that this was something that was that was
not only commonplace, but it was also already being considered
in terms of animal welfare. I know in Great Britain

(27:24):
they already had laws in place by the time the
mouse test was being used about how animals could be
used for medical testing. That was one of the other
things that led to some of the debates around whether
people should adopt the test. It was it was like, yes,
but we're harming animals and you would just realize you
were pregnant in a couple of weeks anyway, right. Um,
So there's a lot of a lot of interesting layers

(27:44):
to it, and it kind of evidence is a discussion
about animal rights that was happening I think earlier than
we maybe think of it exists. Yeah. Well, and that
conversation connects to something that listeners asked us to talk
about before, which is the synthesis of insulince and how
that was developed um, which is like, it's definitely on
the very long topic idealist um and also connects to

(28:08):
some of those questions about the ethics of of animals
in medicine. Yeah. I have a fun postcard from Barcelona. Nice.
It is from our listener Alex uh, and I believe
the other name on here is Tari, although I'm not positive. Uh.
It's written very very tiny and it has been through
international mail. But Alex writes, Dear Holly and Tracy, Hello

(28:32):
from Barcelona. My wife and I are traveling Europe to
celebrate her finishing her master's degree in graphic design. Congratulations.
I have been meaning to come here since first learning
about Lisata familia in seventh grade, so this is something
of a lifelong dream being fulfilled by the way. I
know you two love to shout out educators, so I
would like to thank my middle school Spanish teacher. I

(28:52):
believe that's Senora Savera for inspiring this trip and for
being an incredible teacher. So yes, of course, always always
my it is off to educators. It was fortuitous timing
for me to get to listen to your episode on
Francisco Franco a few days before I left. I have
always found the Spanish Civil War very interesting, but have
only learned about it through fictional works such as Pans

(29:13):
Labyrinth and for Whom the Bell Tolls. I actually got
to discuss Franco a little bit with a tour guide
at a winery, and as a Catalan he had an
interesting perspective as well about how the Franco regime banned
the Catalan language and suppressed the culture. Anyway, thank you
for the great show. So it's a beautiful it's one
of those um a sort of wide postcards, and it's

(29:33):
a really beautiful perspective on the Sagarada Familia uh from
inside and it's just absolutely lovely, So thank you, thank
you again. I'm always wold that people want to stop
while they're traveling beautiful places and write his postcard. It's
quite flattering. Yeah. Uh, if you would like to direct
to us. You can do so at History Podcast at
how stuff works dot com. You can also find us
pretty much everywhere on social media as missed in History,

(29:56):
and you can go to missed in History dot com,
which is our website where you will find every episode
of the show that has ever existed, as well as
show notes for the ones that Tracy and I have
worked on. If you would like to subscribe to this podcast,
I highly encourage it. That would be great. You could
do that on the I Heart Radio app, at Apple Podcasts,
or wherever you listen to podcasts. For more on this

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and thousands of other topics, visit how stuff Works dot com.
M