Dr. J. Davy on the Congelation of Animals. 251 
Experiments made to ascertain the effects produced by poisonous 
substances on the contractions of the yelk are recorded, and the 
general fact ascertained of the extreme indifference to such agents of 
yelk-protoplasm. 
Carbonic acid, however, is shown to destroy the contractility 
rapidly, and chloroform to arrest it for a time. 
The process of cleavage is described, and experiments are given 
which show that oxygen in the surrounding medium is an essential 
condition of its occurrence. The imfluence of heat in quickening it, 
and the comparative indifference which it shows to the action of a 
galvanic current and to most poisons, are proved by a series of experi- 
ments, in which also the remarkable and destructive activity of car- 
bonic acid is evidenced. 
The author has considered the egg as a cell, its contents as a 
protoplasm, of which the firmer cortical layer is the equivalent of 
the primordial utricle, and the fluid food-yelk of the liquid contents, 
while the formative yelk is represented by the granular accumulation 
around the nucleus. Two stages or grades of development of proto- 
plasm are conceived to be represented by the two forms of yelk; 
and a parallelism is attempted to be drawn between them and the 
stages of development through which many amceboid organisms 
pass, and which the author believes to have a wide if not a universal 
existence in the organic world,—the lower grade, represented by the 
homogeneous food-yelk with a cortical layer and possessed of 
rhythmic contractility, passing into the higher, represented by the 
formative yelk, of a granular structure and possessed of a fissile 
contractile property only. 
“On the Congelation of Animals.” By John Davy, M.D., 
F.R.S. &c. Received since the end of the Session. 
In a very interesting and elaborate paper by M. Puget, entitled 
“Sur la Congélation des Animaux,” published in the Number of 
the ‘Journal de Anatomie et de la Physiologie’ for January and 
February of this year, he refers to a statement of mine, made man 
years ago*, that the leech may be frozen without loss of life. The 
experiments which he has instituted, and which appear to have been 
conducted with great care, have led him to an opposite conclusion— 
viz. that congelation is not only fatal to the leech, but to animals 
generally, without a single exception. He considers the cause of 
death (the vera causa, to use his own words) to be an altered con- 
dition of the blood. In consequence of this statement, I thought it 
right to repeat the experiments on the leech, and to extend them to 
some other animals. They were begun at Oxford in May, in the 
laboratory of Professor Rolleston, with the kind assistance of Mr. 
Edward Chapman and Mr. Robertson ; and since then, in the fol- 
lowing month, they have been continued at home in Westmoreland. 
At Oxford the trials were made on leeches and frogs; at home, 
on these animals, and on the toad and some insects. The freezing- 
* Researches Physiol. and Anat. 11. p. 121. 
