Selecting Good Students: Sherrington’s Frog Test

The second paragraph of Sir Vincent Wigglesworth’s (1899-1994) biographical memoir for the Royal Society reads:

His father was imaginative, encouraging his children to collect material for demonstrations such as the microscopic life in a drop of pond water or the circulating corpuscles in the web of a frogs foot. Many years later, V.B.W. mentioned the fascination of the frog preparation to Sir Charles Sherrington, then living in Master’s Lodge at Caius. He said he used it as the ‘acid test’ for identifying research students. Less dedicated students glanced down the microscope and passed on, but future ‘physiologists’ were unable to tear themselves away from the view of blood cells bustling along capillaries. 

I am delighted to report that I unknowingly passed Sherrington’s test too. I was given what was little more than a toy microscope around the age of fifteen and was transfixed first by watching the blood circulation in a tadpole’s tail and then a frog’s web.

An old school friend dug this out of his loft
before moving house earlier this year. We had
identical microscopes made by J & L Randall
under the trading name of SEL (Signalling
Equipment Ltd). The magnification was fixed
at 100x. My father made a case for both of us
but mine along with the microscope have long gone

Sir Charles Sherrington (1857-1942)
(Wellcome Images)

I looked for a good demonstration on YouTube or in commercial libraries; they can be found with a simple Google search. However, I was disappointed since the magnification used is sometimes too great and the ability to rack the focus up and down is missing. The extraordinary contortions of the red cells are evident as well as some of the jostling as vessels branch. But there is nothing like the real experience.

In the Wellcome Library’s collection I did find an old gem, made in 1923, shot in black-and-white. One of the photographers was August Krogh (1974-1949), the Nobel Laureate famous for his work on control of capillary circulation. 

Liddell EGT. 1952. Charles Scott Sherrington 1857-1952. Biographical Memoirs of Fellows of the Royal Society 8,  241-270

Locke M. 1996. Sir Vincent Brian Wigglesworth, C. B. E., 17 April 1899 - 12 February 1994. Biographical Memoirs of Fellows of the Royal Society 42, 541-553.