“Founded on pioneer research, supported by rare skill in execution, inspired by the highest ideals, this company has always endeavored to make instruments a little better than those already produced, to set a standard a little higher than that already attained. (Spencer Lens Company, 1929) Copyright January 1, 1929- Spencer Microscopes, Microtomes and Accessories

A pathologist that I worked with asked if I wanted an old AO microtome (American Optical/Spencer). His mentor pathologist gave it to him and now he wanted to give it to someone who would appreciate it. I, of course, am a “Histology Nerd”. I whole heartedly agreed and was so excited. An old AO microtome!

He asked to transfer it in the garage as it is quite heavy. Of course, all microtomes are heavy. Oh no, this was beyond heavy and not what I was expecting. I was expecting an AO 820 manual rotary microtome. This is an AO 860 Sliding microtome! What a find!

I am in awe of such an invention, but then what should I do with it? It is old, dirty and taken apart. It needs a lot of cleaning and how do I put it back together? This is really too heavy (over 80 lbs) to be taken anywhere. My husband really doesn’t want to move it.

I thought of donating it to a scientific museum. I found Indiana Medical History Museum (https://www.imhm.org/) and I got all of the paperwork, but I didn’t want to let it go. This was a piece of history. Histology History! Patients were diagnosed, breakthroughs and cures were found on this microtome. I didn’t want to put it in the basement and let it collect dust. I started doing some research on American Optical 860 Sliding Microtome with my fingers crossed. I found a manual “The Effective Use and Proper Care of The Microtome” by Oscar W. Richards, Ph.D. , Chief Biologist, American Optical Company. Section V “Directions for the use of the AO Spencer No 860 Sliding Microtome” and the Spencer Lens Catalog Microscopes, Microtomes and Accessories. Who is Spencer?

The American Optical 860 Sliding Microtome was actually made by Spencer Lens Company. American Optical bought the Spencer Lens Company in 1935 and by 1945 it was known as the Instrument Division of American Optical Company (AO History, 2006). This microtome is designed to cut sections of accurate thicknesses, one section after another being the same thickness, of not only the soft tissue usually cut but of the harder tissue usually found very difficult to cut on any microtome. It will also cut section of large diameter (3 ½”) one after another until 1 1/8” of the object is consumed without the necessity of lowering the object and resetting the feed for further sectioning. (Spencer Lens Company, 1929).

I have been mostly cutting clinical but I do have experience in veterinary. I had to cut a cow’s optic nerve once. Microtomy wasn’t hard, it was the large mold with the small chuck. Adaptation took place. I’ve only used manual and automatic rotary microtomes.

There are two basic types of paraffin microtome: rotary and sliding microtome. Rotary microtome transforms the rotation movement into an up and down movement of the sample, and in each upward movement, the sample holder draws near the sample toward the blade a distance selected by the user. The holder has built in a mechanism to orientate the surface of the sample relative to the blade. During sectioning, the blade maintains a fixed position, but the initial position and angle can be regulated. This angle is the angle of the blade with respect to the surface of the sample block. A sliding microtome is able to cut sections by moving the blade over the sample holder, or the other way around. The movement is by hand, forward and backwards. It is before the starting of the forward movement when the paraffin block is raised, or the blade lowered a selected distance, that gives a section thickness.

Rotatory and sliding microtomes have both advantages and disadvantages. Rotatory microtomes are more precise and get uniform sections more easily. Some rotatory microtome models come with an electric engine for automatic sectioning. The mechanics of sliding microtomes is simple and the disposition of the pieces allows obtaining sections from larger surfaces (larger paraffin blocks). Celloiding blocks (another embedding medium) can be cut in these microtomes. However, sliding microtomes are not used much in histology labs nowadays (University of Vigo, Spain, 2019)

So who else was using the sliding microtome? I found three other AO 860 microtome article summaries:

1. A Southeast U.S.A. asphalt, NO. 6 was used in this study. An asphalt specimen was prepared by pouring the molten asphalt into a small aluminum weighing dish to a depth of about 625mu. A 3.8-cm diam microtome specimen holder was then embedded into the soft asphalt. Upon cooling, the asphalt was cut the diameter of the specimen holder and the surface was shaved smooth with a microtome (Spencer, Model 860) (United States, National Bureau of Standards, 1964)

2. A Western Michigan University chemical and paper engineering senior thesis used an American Optical Company Spencer 860 Sliding Microtome to section their papers. This entire operation was carried out at a constant humidity (50% R.H.) and temperature (72^o F)…The wooden block was clamped into the microtome and leveled by gradually raising the block 5 mu increments (Beer, 1963).

3. There is a distinct advantage in the use of whole sections of the human brain in the neuroanatomy teaching laboratory and for examination in neuropathology. This is particularly true in the study of structural relationships which can not be appreciated when a small block of tissue is cut out of the brain and is examined as an isolated part. The major deterrent to more extensive use of such preparations is the cost of a large microtome customarily employed for cutting the whole brain. Even when available, as in our laboratory, such a microtome is difficult to operate, sometime requiring two technicians. (Brody, 1973)

After some Googling, this sliding microtome is still in use and there are still many on sale today! I was shocked! Found one saying, “It is a fine instrument, ideal for accurately cutting hard objects such as bone, wood, frozen, celloidin, and paraffin preparations…Cutting thickness is adjustable from 1 to 40 microns (Rankin Biomedical, 2020).”

That is amazing. When they spoke of using hard objects, I never thought of using asphalt, but they did. I have so much more respect for the AO 860 sliding microtome used in the past and the ones that are still working today. I don’t have an “antique”, I have a “hero”. Thanks to the manual and soon she will be cleaned up and ready for microtomy.

References

AO History. (2006). Retrieved from https://user.xmission.com/~psneeley/Personal/AOHistory.htm

Beer, J. J. (1963). Filler Distribution as Effected by Drainage Rate and Volume. Retrieved from Western Michigan University: https://scholarworks.wmich.edu/cgi/viewcontent.cgi?article=1098&context=engineer-senior-theses

Brody, H. (1973). Adapting the Spencer 860 Microtome to Cut Entire Section of Human Brain . Retrieved from Stain Technology 48:6, 347-348: https://www.tandfonline.com/action/showCitFormats?doi=10.3109%2F10520297309116654

Rankin Biomedical. (2020). American Optical 860 Sliding Microtome. Retrieved from Rankin Biomedical: https://rankinbiomed.com/product/refurbished-american-optical-860-sliding-micrtome/

Spencer Lens Company. (1929). Catalog of the More Popular Spencer Microscopes, Microtomes and Accesssories. Buffalo, New York.

United States, National Bureau of Standards. (1964). Engineering and Istrumentation. C., Volume 67. Journal of Research, 122. Retrieved from https://books.google.com/books?id=BXEoAQAAIAAJ&pg=RA1-PA122&lpg=RA1-PA122&dq=spencer+860+microtomes&source=bl&ots=CeFLxg-8to&sig=ACfU3U318BJlOBYrY2KBycI4NL7wr2DPHA&hl=en&sa=X&ved=2ahUKEwitn_bJtJLrAhWBB50JHessDIE4KBDoATAFegQIChAB#v=onepage&q=spencer%20860%

University of Vigo, Spain. (2019, 7 24). Paraffin Microtome. Retrieved from Atlas of Plant and Animal Histology: https://mmegias.webs.uvigo.es/02-english/6-tecnicas/4-mparafina.php