ARTICLE If: 
EXPERIMENTS AND OBSERVATIONS UPON THE CIRCULATION IN THE SNAPPING TURTLE (CHELONURA 
SERPENTINA), WITH ESPECIAL REFERENCE TO THE PRESSURE OF THE BLOOD 
IN THE ARTERIES AND VEINS. 
By 8. Wzrr Mircnueun, M.D., 
Lecturer on Physiology. 
Read October 18th, 1861.* 
Since the experiments of Hales in 1731, and the later and more accurate researches of 
Poiseuille, a number of observers have studied the blood-pressures in various vertebrate 
animals, among which may be mentioned the horse, dog, sheep, cat, rabbit, and bird. 
So far as I can discover, the only observations of this nature upon cold-blooded vertebrata 
were made by Volkmann, who experimented upon frogs and fresh-water fishes. No other 
similar examination of blood-pressures appears to have been made, and up to the present 
date no one has studied the subject in connection with reptiles of any kind. 
The object of this memoir is to exhibit the results of a series of researches upon the 
blood-pressure in one of the most vigorous members of this class, the Chelonura serpen- 
tina, and thus to fill an important gap in our knowledge of hemometry. The reptile in 
question is admirably suited for this purpose. It is strong, active, singularly tenacious 
of life, and may be procured easily of any weight up to twenty-five or thirty pounds. 
Inhabiting the waters of many of the streams and mill-dams in the Middle States, it may 
be readily had in excellent condition during the spring and summer, and for all purposes 
of physiological and toxicological research, may be made use of whenever it is desirable 
to replace the frog by an animal of greater bulk and superior tenacity of life. 
The Snapping Turtles used in the following researches were brought from Havre de 
Grace on the Susquehanna river, and from the lower part of the State of Delaware, care 
being taken that only such were employed as had been captured by hand (dug out of the 
mud), rather than such as had been taken by the hook and line. 
As I have alluded to the great strength and tenacious vitality of these creatures, it may 
be well to make some brief statement of a more distinct nature as to the extent to which 
they are endowed with these qualities. 
A Snapper weighing twenty-seven and a half pounds was fastened by its tail to a ring, 
* Published in April, 1862. 
