Dr. Davy on the Congelation of Animals, 



253 



10. A cockroach, a flesh-fly, and a minute insect, an ichneumon* 

 (Ccelineus niger ?), confined together in a small glass tuhe, were kept some 

 minutes in the mixture. Thawed, they were found all three dead. 



These results, so far as the particular instances are concerned, are suffi- 

 ciently confirmatory of M. Puget's, and on my mind they leave little 

 doubt that his general proposition (his inference from his very numerous 

 experiments) is correct, that congelation is fatal to animal life. It is 

 hardly worth while to attempt to account for the different conclusion I 

 had come to, that referred to by him relative to the leech, it being partly 

 founded on the fact that leeches which had been enveloped in ice for many 

 days were not thereby killed, and partly on witnessing some marks of 

 vitality in leeches which were believed to have been artificially frozen, and 

 which very soon after died. 



Whilst admitting that congelation, thorough congelation of an animal is 

 incompatible with life, the cause of death from congelation seems open to 

 question, and more especially that assigned by M. Puget as the vera causa, 

 a change in the blood, and chiefly in its corpuscles. That these corpuscles 

 are changed by freezing in form and condition seems to be certain. Before 

 seeing M. Puget's paper I had ascertained the fact, and not only that the 

 corpuscles were changed, but also that the entire blood was to some extent 

 altered, leading me at the time to ask whether some of the injurious 

 effects of frost-bite may not be mainly owing to the freezing of the blood, 

 and the changes in consequence in the corpuscles and in a less degree in the 

 fibrin t ; and since, in examining the blood of the animals exposed to the 

 freezing mixture, I have had this confirmed ; but the change in these in- 

 stances was comparatively slight ; even in those of the congealed limbs of 

 the frogs and toad the majority of the corpuscles appeared little altered ; 

 some few seemed ruptured, some corrugated, and more contracted. 



Judging from the effect of congelation on the heart of the frog in ex- 

 periment No. 5, and from the effects of congelation partially produced, as 

 in the extremities of the frog and toad, I would rather attribute the death 

 to the freezing of the organs, not excluding the blood, than to the freezing 

 of the blood alone ; and I would ask, is not this view most in accordance 

 with the pathology of the subject, with all that we know of frost-bite and 

 its consequences in man, and with the results of Mr. Hunter's experiments 

 on the local effects of congelation in animals — those on the ear of the 

 rabbit and wottle of the cock J ? and do not some even of M. Puget's results 



* For the name of this insect I am indebted to Dr. Gray, F.R.S. It was selected on 

 account of its minuteness : it weighed hardly of a grain ; it seemed probable, on 

 account of the minuteness of its vessels, that its fluids might escape congelation after 

 the manner of fluids in capillary tubes, which may be reduced many degrees in tempera- 

 ture without being frozen. 



t Physiological Eesearches, 1863, p. 371. See also Trans, Royal Society of Edin- 

 burgh, 1865, vol. xxiv. p. 26. 



; Phil Trans. 1778, p. 34. 



