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History of Early Microscopes

00:00:14.04 My name is Joe Gall.
00:00:15.25 I'm at the Carnegie Institution Department of Embryology
00:00:19.06 in Baltimore,
00:00:21.08 and I'm going to talk to you today
00:00:24.02 about the development of the microscope
00:00:26.11 and its relationship to the discovery of the cell.
00:00:30.23 It's well known that the discovery of the cell and its parts
00:00:35.11 depended crucially on the development of the compound microscope,
00:00:41.11 and yet the microscope was invented
00:00:44.29 in 1600,
00:00:46.28 but it wasn't for more than 200 years after that
00:00:50.18 that the cell was discovered,
00:00:53.22 and even another 50 years or so
00:00:56.15 before the nucleus
00:00:58.28 or specifically the chromosomes
00:01:01.11 and other parts of the cell
00:01:03.02 were properly discovered and elucidated.
00:01:06.11 So, what I want to do today
00:01:08.21 is to discuss why this was
00:01:11.17 and what was the relationship
00:01:13.24 between the development of the microscope
00:01:15.27 and early studies on the cell.
00:01:18.11 So, I can start
00:01:21.27 by talking about what was actually discussed...
00:01:26.06 what was actually discovered in 1600.
00:01:31.21 And what happened in 1600 was that
00:01:36.14 it had been known for quite a long time,
00:01:38.28 actually for hundreds of years,
00:01:41.01 that one could magnify an object
00:01:44.20 with a single lens held close to the eye.
00:01:48.04 Lenses of that sort had been made since at least the 14th century.
00:01:53.10 And these were called magnifying glasses,
00:01:56.23 for obvious reasons,
00:01:58.21 and sometimes called simple microscopes.
00:02:02.00 So, a simple microscope
00:02:03.23 is a single lens
00:02:05.25 and it forms a virtual image of the specimen
00:02:07.28 on the retina of the eye.
00:02:09.23 In other words, there's no image other than that
00:02:13.14 which is inside the eye on the retina.
00:02:17.22 Now, that single lens can be used in a different way.
00:02:21.23 By being put close to the object,
00:02:25.04 a real image of the object
00:02:27.20 can be formed at a distance
00:02:30.08 from the lens on, say,
00:02:32.24 a sheet of paper or some other object.
00:02:37.04 So, the real image,
00:02:39.24 which is in space,
00:02:42.19 can then be viewed with another lens,
00:02:47.25 the second lens being used
00:02:50.19 simply as a magnifying glass
00:02:52.19 to magnify the real image
00:02:55.05 that had been formed by the first lens.
00:02:57.06 Now, that is all there is, in principle,
00:03:00.09 to a compound microscope,
00:03:02.15 and that is what was invented in 1600.
00:03:05.13 Now, that doesn't look much like a microscope,
00:03:07.25 but if you put a tube around it,
00:03:09.24 now it does begin to look like a microscope.
00:03:12.26 So, as I said, this was invented around 1600.
00:03:17.13 We don't really know precisely who did it,
00:03:21.09 but at the same time a combination of two lenses
00:03:25.02 of this sort
00:03:27.20 constitutes a telescope.
00:03:29.14 It depends on the sizes of the lenses
00:03:31.10 and their relative spacing
00:03:33.04 whether you have a telescope or a microscope.
00:03:35.05 So, these two instruments were both invented,
00:03:38.06 essentially at the same time,
00:03:40.10 by an unknown spectacle maker
00:03:43.15 in Holland at around 1600.
00:03:46.25 Now, the compound microscope
00:03:51.13 looks like my diagram
00:03:54.19 if you take, for example,
00:03:57.21 the microscope of Robert Hooke
00:04:00.22 from his book in 1665.
00:04:04.05 You can see that there is a tube,
00:04:07.17 and in fact there is one lens at the bottom, down here,
00:04:13.11 a small lens which does most of the magnification,
00:04:16.01 and then there's a larger lens
00:04:18.10 up here at the top,
00:04:20.04 which is the eye lens.
00:04:22.14 So, in fact, there are two lenses in that microscope,
00:04:25.21 just exactly like this one diagrammed here.
00:04:30.06 Now, the interesting this is that
00:04:36.12 the telescope was made
00:04:42.23 immediately afterwards the 1600s discovery,
00:04:46.12 and Galileo made a telescope,
00:04:49.26 which is still in existence,
00:04:52.04 and this is a photograph that I took
00:04:54.12 of Galileo's original telescope,
00:04:59.01 and by 1610 Galileo
00:05:02.16 was looking at the stars, the moon
00:05:05.06 -- he saw the craters on the moon for the first time --
00:05:07.25 he saw the satellites of Jupiter
00:05:12.03 circling the plant,
00:05:14.20 and realized that they were circling Jupiter
00:05:17.13 in the same way that our moon was circling our planet,
00:05:21.05 the planet Earth.
00:05:23.07 He basically did all of this within a year or two.
00:05:27.03 He published a very famous book.
00:05:29.16 He revolutionized astronomy.
00:05:31.12 And it all happened within 10 years
00:05:34.06 of the development of the telescope.
00:05:36.14 Now, the curious thing is that
00:05:38.26 although the microscope
00:05:42.00 was essentially invented at the same time,
00:05:45.28 there's almost no information
00:05:49.02 gleaned by the use of microscopes
00:05:51.01 for quite a long time afterwards.
00:05:54.03 Now, it's know that Galileo
00:05:55.25 actually made a microscope himself,
00:05:58.05 and it's unfortunate that that microscope
00:06:00.14 is no longer in existence,
00:06:02.23 because it would be very interesting to know exactly
00:06:05.07 what he did make,
00:06:07.27 but curiously the very first image
00:06:11.08 of anything taken with a microscope,
00:06:13.23 a compound microscope,
00:06:15.17 was published 30 years after the discovery
00:06:18.13 in 1630,
00:06:21.12 and that image is this one.
00:06:23.28 It's a picture of three bees,
00:06:26.21 three honey bees.
00:06:28.29 It was published by a man named Francesco Stelluti
00:06:32.04 in 1630,
00:06:34.02 and there are a lot of interesting things about this image.
00:06:36.22 In the first place,
00:06:38.21 Stelluti was not writing a text about biology,
00:06:41.23 but it was a translation
00:06:44.03 of some Latin poems that had nothing to do with bees.
00:06:48.02 And this image
00:06:50.11 may have been taken
00:06:53.01 with the microscope made by Galileo -
00:06:55.18 we don't know that, but it's possible.
00:06:57.16 We don't know much more about this image
00:06:59.16 except that it's in this book,
00:07:02.03 quite strangely,
00:07:03.24 because as I said the book has nothing to do with biology,
00:07:06.26 it's a book of poetry.
00:07:08.22 What is very interesting
00:07:10.17 and would be recognizable immediately
00:07:12.02 to a historian of art
00:07:14.02 is that three bees in this configuration
00:07:18.16 represents the coat of arms
00:07:21.07 of the Barberini family,
00:07:23.21 of which the Pope was a member,
00:07:25.19 and in fact this image
00:07:29.16 was more a solicitation of interest of the Pope
00:07:32.17 than it was a biological study
00:07:36.12 of honey bees.
00:07:37.22 At any rate,
00:07:40.20 the next image of objects
00:07:44.01 taken with a compound microscope,
00:07:46.09 remarkably enough,
00:07:48.10 is another 30 years.
00:07:50.12 In 1665, we have the magnificent book
00:07:53.28 published by Robert Hooke,
00:07:55.16 in England,
00:07:57.00 called the Micrographia,
00:07:59.16 a set of 38 plates
00:08:03.09 showing different types of objects
00:08:05.12 taken with a compound microscope,
00:08:07.21 most of which are biological in nature.
00:08:10.01 And one of the most famous of those images
00:08:12.15 is this one of cork cells,
00:08:15.18 and this is the image
00:08:19.00 which is always used as
00:08:23.13 illustrating the discovery of cells,
00:08:25.14 but that's actually a little bit misleading,
00:08:27.17 because although Robert Hooke
00:08:30.03 saw these cells in the cork
00:08:33.15 and he gave them the name "cell",
00:08:36.08 he was actually referring to a cell
00:08:38.26 in the simple sense of a box
00:08:41.28 or a prism cell
00:08:43.29 or some other square object.
00:08:45.18 He was using it as an anatomical
00:08:48.01 or morphological description
00:08:50.16 of what he saw,
00:08:52.06 not that he had any concept
00:08:54.22 that tissues of animals and plants
00:08:57.17 are composed of what we now know as cells.
00:08:59.24 So it's a little bit misleading to say that
00:09:02.01 Robert Hooke discovered cells,
00:09:03.17 but nevertheless this is his image
00:09:05.14 and it's quite famous.
00:09:07.10 But the important point here
00:09:09.27 is that it's 65 years
00:09:12.14 after the so-called invention of the microscope,
00:09:16.11 compound microscope,
00:09:19.04 and one wonders,
00:09:20.24 why did it take so much time?
00:09:23.16 Among other things that Robert Hooke drew
00:09:27.05 is a very famous image of the flea.
00:09:30.10 This is a beautiful drawing,
00:09:34.22 at least 15 inches or so in size
00:09:38.00 as a fold-out in his book,
00:09:42.02 the Micrographia.
00:09:44.00 Now, as I said,
00:09:46.27 this is 65 years
00:09:49.15 after the invention of the microscope
00:09:52.12 and one can ask,
00:09:55.10 what's going on here?
00:09:57.15 Why are there not more
00:09:59.25 biological images of objects
00:10:03.05 taken with a microscope
00:10:05.04 if this invention was so important?
00:10:08.24 Well, the answer is
00:10:12.14 really something to do with
00:10:16.17 the optics of these instruments.
00:10:20.07 What was invented
00:10:23.01 was the use of two lenses
00:10:25.24 to form a magnified image,
00:10:28.10 as we now know as a compound microscope.
00:10:34.01 Now, lenses have a serious problem
00:10:39.18 caused by their shape.
00:10:43.15 All lenses that were possible to grind
00:10:48.20 at that time in the 17th century,
00:10:51.04 or even today,
00:10:54.02 have either a spherical surface
00:10:56.24 or a plane surface.
00:10:58.23 In other words, you can grind lenses
00:11:01.08 that have a plane surface,
00:11:03.06 a spherical surface,
00:11:05.12 or one of each,
00:11:07.08 or two spherical surfaces,
00:11:09.04 but that's all you can do.
00:11:11.22 And it is a simple fact
00:11:15.15 that a spherical surface
00:11:17.23 does not produce a perfect image
00:11:19.28 of an object.
00:11:21.14 In fact, it only forms a good image
00:11:24.12 near the center of the lens,
00:11:26.28 and the further away that you go
00:11:29.21 from the center of the lens,
00:11:31.08 the poorer the imaging quality of the lens is.
00:11:37.00 This is known as spherical abberation.
00:11:40.28 If you put two lenses together,
00:11:43.11 they have more spherical abberation
00:11:45.12 than one lens.
00:11:47.09 So, in fact, a compound microscope,
00:11:49.28 with its two lenses,
00:11:51.23 has more spherical abberation than a single lens.
00:11:56.22 So, why was the invention of the microscope
00:12:00.14 such an important thing?
00:12:02.06 Well, it was important because
00:12:05.29 it allowed you to use a convenient instrument
00:12:11.01 to form a medium-magnification image
00:12:17.06 of an object such as a flea
00:12:20.01 or other relatively large objects.
00:12:22.18 So see even smaller objects, however,
00:12:26.18 the lenses had to be made smaller and smaller,
00:12:31.06 and when you had two lenses together
00:12:34.21 of that sort
00:12:36.24 the spherical abberation was so bad
00:12:38.22 that the images became essentially unusable.
00:12:42.22 So, what's the solution to that problem?
00:12:44.15 Well, the solution to the problem
00:12:46.06 is actually to go back to
00:12:48.23 the simple microscope, the single lens,
00:12:52.03 make it smaller and smaller,
00:12:54.23 and put it very close to the eye.
00:12:58.09 That way, one can actually see
00:13:01.14 very small objects more clearly
00:13:04.03 than one can see through a compound microscope.
00:13:07.02 Now, this was not really appreciated
00:13:10.25 in the theoretical sense,
00:13:12.11 but it was certainly appreciated in a practical sense,
00:13:16.03 and the highest magnification objects
00:13:19.26 that were looked at
00:13:22.24 were actually looked at with simple lenses,
00:13:25.18 single lenses, simple microscopes,
00:13:28.20 not compound microscopes.
00:13:30.22 And the most famous of these
00:13:33.03 was the microscope
00:13:35.08 used by Antonie van Leeuwenhoek,
00:13:38.04 a Dutch investigator who lived around...
00:13:42.24 well, who lived from the mid-1600s
00:13:45.08 to the early 1700s.
00:13:47.20 And Leeuwenhoek
00:13:50.09 invented this microscope, shown here,
00:13:54.29 which is rather complicated-looking.
00:13:58.07 It's a small instrument, just a couple of inches high.
00:14:03.13 And the critical part of this microscope
00:14:05.18 is shown right there by the arrow,
00:14:07.27 is a tiny, tiny lens,
00:14:10.18 only a millimeter or so in diameter.
00:14:14.09 Now, this microscope is extremely difficult to use
00:14:17.12 because you have to put it right up to your eye,
00:14:21.23 within a centimeter of so of your eye,
00:14:26.22 and you have to mount the object on a pin,
00:14:31.03 which is shown here...
00:14:34.04 this is the pin,
00:14:36.06 the lens would be approximately here,
00:14:38.29 from the side view,
00:14:41.13 and then from the face-on view
00:14:43.19 the lens is right here.
00:14:45.19 So, this thing is difficult to use,
00:14:49.03 but it actually produces
00:14:51.06 a much better image than a compound microscope.
00:14:54.29 And so Leeuwenhoek
00:14:57.04 was able to see bacteria,
00:14:59.29 protozoa,
00:15:01.23 cilia and flagella,
00:15:03.17 and sperm for the first time.
00:15:05.26 And this is his illustration of bacteria
00:15:11.10 in the mouth.
00:15:13.13 As you can see in the Latin, here,
00:15:16.27 he says gingiva mea,
00:15:20.10 that's his mouth,
00:15:22.03 and down here it says saliva, salivae,
00:15:27.12 and animalcule,
00:15:29.13 those are the little animals
00:15:31.18 that were crawling around in his mouth
00:15:33.22 - these are bacteria.
00:15:35.19 So, Leeuwenhoek was able to see bacteria,
00:15:39.17 not with a compound microscope,
00:15:41.01 but with a simple microscope,
00:15:42.16 a single lens,
00:15:44.05 a very tiny lens
00:15:46.01 in which the spherical abberation
00:15:47.28 was less than in the compound microscope.
00:15:50.25 So, this is a well-known fact
00:15:54.11 to anyone who studies the history of microscopy,
00:15:57.11 but it's been more or less overshadowed
00:16:00.28 by the fact that the compound microscope,
00:16:05.09 in the 19th century,
00:16:06.28 was developed to the point
00:16:09.18 where one could get the same degree of resolution
00:16:13.19 as had been accomplished with the simple microscope
00:16:18.09 in the 17th and 18th centuries.
00:16:21.13 So, curiously enough,
00:16:23.15 the most important advances
00:16:28.24 in observing small biological objects
00:16:32.07 came with simple microscopes,
00:16:34.14 not with compound microscopes,
00:16:36.14 in these early days.
00:16:38.07 So, here's another example in 1760.
00:16:42.06 This is the so-called Screw-Barrel microscope,
00:16:45.17 and again here are the specimens
00:16:48.14 mounted on a slide, here,
00:16:50.22 which can be moved back and forth.
00:16:52.22 It has a single lens,
00:16:55.12 again shown by the arrow,
00:16:58.09 and you put this thing up close to your eye,
00:17:00.25 that is you put your eye very close
00:17:02.28 to this region right here,
00:17:04.29 to look through it.
00:17:07.09 And interestingly enough,
00:17:09.17 we come even into the 19th century
00:17:14.05 and here we show
00:17:18.00 a slide of onion root tip
00:17:22.21 in which one can see the cells,
00:17:27.15 and in addition one can see the nuclei in these cells
00:17:31.00 - here's a black...
00:17:33.07 a more or less darkened area,
00:17:34.25 which is the nucleus of this cells,
00:17:36.25 then the nucleus of this cell is up here.
00:17:39.26 So, these are cells with nuclei.
00:17:43.01 Now, the nucleus of the cell
00:17:45.16 was discovered by Robert Brown in 1833,
00:17:50.19 and this is an image taken
00:17:53.06 of a modern microscope slide
00:17:55.16 with Brown's microscope.
00:17:58.29 One might imagine that Brown
00:18:01.13 was using a compound microscope,
00:18:03.07 but he was not.
00:18:04.24 He was using a simple microscope
00:18:06.09 as late as 1830,
00:18:08.16 in which he discovered the cell nucleus.
00:18:13.03 And this Robert Brown's actual microscope.
00:18:15.11 It's still in existence
00:18:18.03 and, again, it has a single lens up here
00:18:22.07 and the specimen is mounted down lower,
00:18:26.26 on this stage right here.
00:18:29.27 The lens could be moved up and down
00:18:32.21 on a rack
00:18:35.03 at this point right here,
00:18:38.09 and focused onto the object.
00:18:40.03 But even as late as 1830,
00:18:42.12 the best observations on cells
00:18:45.08 were being made with simple microscope,
00:18:47.13 not with compound microscopes.
00:18:50.01 Now, what happened in the 19th century
00:18:54.05 was that techniques, optical techniques,
00:18:59.19 were discovered
00:19:02.13 to get rid of spherical abberation in the lens...
00:19:07.06 I should say to make combinations of lenses
00:19:10.01 which got rid of the spherical abberation,
00:19:12.11 and also to get rid of chromatic abberation,
00:19:15.24 another problem that I have not discussed.
00:19:19.00 Chromatic abberation
00:19:21.22 arises from the fact that
00:19:25.11 a lens forms images of an object
00:19:29.28 in different colors at different distances,
00:19:32.23 in other words the red part of the object
00:19:34.20 is focused at a different distance
00:19:36.03 than the blue part,
00:19:38.01 and so that means that not only do you have
00:19:41.10 spherical abberation,
00:19:43.12 which is a general fuzziness of the image,
00:19:45.21 but you have the blue parts of the image focused in one place
00:19:48.06 and the red parts focused in another.
00:19:50.23 So, these problems with chromatic and spherical abberation
00:19:54.00 were actually first addressed
00:19:57.12 in the 19th century,
00:19:59.02 and so it really wasn't until the 19th century
00:20:02.01 that compound microscopes
00:20:05.17 became better than single microscopes
00:20:08.20 or single lenses,
00:20:11.28 very small lenses of the sort of
00:20:18.23 that Leeuwenhoek used in the 1700s.
00:20:22.11 So, the history of microscopy in the 19th century
00:20:29.22 involves the making of microscopes
00:20:33.16 in which chromatic and spherical abberation was eliminated,
00:20:37.07 so that finally the compound microscope
00:20:40.04 became better than the simple microscope,
00:20:42.23 and now people were able to see cells and nuclei,
00:20:48.13 and the cell theory was first enunciated
00:20:51.23 in the 1830s, 1838 in fact,
00:20:56.16 by Schleiden and Schwann.
00:20:59.04 So that, even though we give credit to Hooke
00:21:03.10 in one sense for discovering cells,
00:21:05.23 he really didn't have any conception
00:21:08.09 of the cell as a unit of organization
00:21:10.13 of plants and animals.
00:21:12.09 That came with the discussions and experiments
00:21:15.21 and observations
00:21:18.26 of Schleiden on botanical specimens
00:21:20.21 and Schwann on animal cells.
00:21:24.28 This particular image here
00:21:26.28 is of plants cells taken by Schleiden in 1838.
00:21:32.12 So, with the improvement of the compound microscope
00:21:36.14 during the 19th century,
00:21:38.20 it became necessary
00:21:40.28 to make slides and preparations
00:21:46.12 of cells and tissues
00:21:50.18 which were adequate to the new, improved
00:21:53.20 ability of the microscope.
00:21:55.02 So, the 19th century
00:21:57.03 was really the time
00:22:00.19 when it was discovered how to fix cells
00:22:03.11 and tissues,
00:22:05.02 how to embed them,
00:22:06.24 how to cut thin sections of them,
00:22:09.08 and particularly how to stain them
00:22:11.24 so that you could see the different parts.
00:22:14.07 And curiously enough,
00:22:17.03 even though the cell theory
00:22:19.03 was advanced in 1838,
00:22:20.23 and the nucleus had been discovered
00:22:22.28 a few years earlier by Robert Brown,
00:22:27.04 chromosomes,
00:22:29.18 mitosis,
00:22:31.23 and all of the finer points of the cytoplasm of the cell
00:22:35.10 were only discovered
00:22:38.06 in the latter part of the 19th century,
00:22:41.18 when the compound microscope in fact
00:22:44.07 came to its perfection.
00:22:48.10 And the development of the microscope
00:22:52.14 is really linked very closely
00:22:55.13 with a man name Ernst Abbe
00:22:59.04 who, in the 1880s,
00:23:01.22 finally developed microscope objectives
00:23:05.03 which were theoretically as good
00:23:09.12 as could be made,
00:23:11.21 according to light optical theory,
00:23:15.19 and lenses of the sort that Abbe
00:23:18.19 first made in the 1880s
00:23:21.14 were made essentially identically
00:23:23.27 right up to the present time.
00:23:26.16 And so I'm showing here
00:23:29.22 an image published by Abbe in 1888.
00:23:33.26 This is of a diatom,
00:23:35.28 a small single-celled organism
00:23:37.29 which has a skeleton made out of silica.
00:23:42.08 This is a low power view
00:23:44.06 of one of these organisms.
00:23:46.07 At higher magnification,
00:23:47.22 you can see the decorations
00:23:49.13 in the silica shell of this organism,
00:23:52.09 and what you can tell
00:23:54.04 by measuring the spacings of these holes
00:23:57.10 in the shell
00:23:59.24 is that Abbe had achieved resolution
00:24:02.19 which actually matched the theoretical limit
00:24:06.24 set by the wavelength of the light
00:24:10.03 that he was using,
00:24:12.04 and microscopes really have not,
00:24:14.12 until very recently,
00:24:17.04 exceeded the limit set
00:24:23.02 by the type of microscope that Abbe invented
00:24:25.24 in the 1880s.
00:24:27.19 So, what we see is that,
00:24:29.08 although the compound microscope
00:24:31.11 was theoretically invented in 1600,
00:24:35.27 it provided only a way of looking at large objects
00:24:40.27 at relatively low magnification
00:24:43.12 throughout the 1600s, 1700s,
00:24:45.06 and even into the 1800s,
00:24:48.13 and that the real use of the compound microscope
00:24:50.19 didn't come until the mid- and late-1800s,
00:24:56.28 with the improvements
00:24:59.15 that corrected the spherical abberation
00:25:01.19 and the chromatic abberation.
00:25:03.22 So, that's the curious history of cell biology
00:25:07.05 and why, in a sense,
00:25:10.29 there was this huge lag in time
00:25:13.27 between the so-called invention of the compound microscope
00:25:17.22 and the development of our more or less
00:25:21.00 modern view of the cell,
00:25:23.29 which came not until about 1900.

This Talk
Speaker: Joseph Gall
Audience:
  • General Public
  • Educators of H. School / Intro Undergrad
  • Student
  • Educators of Adv. Undergrad / Grad
  • Researcher
  • Educators
Recorded: January 2014
More Talks in Microscopy Series
All Talks in Microscopy Series

Talk Overview

Joseph Gall takes us through the history of early microscopes and the discovery of the cell. Compound microscopes were invented alongside the telescope in the 17th century; however these microscopes were not widely used until the late 19th century due to optical aberrations. In the meantime, simple microscopes were used throughout the 1700s and 1800s to make major discoveries in biology, including the first descriptions of the nucleus, cilia, cells, bacteria, and protozoans. Once optics improved in the mid to late 1800s, compound microscopes were used to discover chromosomes, mitosis, and other cellular structures.

Speaker Bio

Joseph Gall

Joseph Gall

Joseph Gall is a Professor at the Carnegie Institution for Science and is a leader in the field of cell biology. He has spent much of his career studying the nucleus and its contents, and has made numerous significant contributions to our understanding of chromosome structure and function. Gall, a distinguished microscopist, is one of the… Continue Reading

Playlist: Microscopy Series

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