Dr. J. Davy 07i 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 indiiFerence 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 influence 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 amoeboid 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 Congelation des Animaux," published in the Number of 

 the • Journal de 1' Anatomic et de la Physiologic ' for January and 

 February of this year, he refers to a statement of mine, made many 

 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 RoUeston, 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- 

 * Research^ Physiol, and Anat. ii. p. 121. 



