Death from Cold in Mammals.

Waikato Times, Volume XXII, Issue 1863, 14 June 1884, Page 2 (Supplement)

Death from Cold in Mammals.

The behaviour of protoplasm under the influence of different degree 3 of temperature is still unsufficiently kfiown. We are familiar with the general ' fact 3 that excessive heat or cold brings about death, and that fever is attended with increased tissue changes ; and in some measure we understand the kind of ■way in which this happens ; but that is all. MM. Richet and Rondeau have studied the influence o£ cold on some mammals. They have adopted a method by which the temperature of animals has been gradually lowered. Dogs resist cold so well that no experiments were made on them. Rabbits were chiefly employed in these investigations. These animals were shaved and surrounded with flexible pewter tubeß, through which cold water was made to circulate. When the temperature of the body was lowered to 25deg. C, respiration began to be ineffectual. The rhythm was not modified ; but the amplitude of the inspirations was chiefly diminished. The functions of the nervous system were much abated when the temperature fell to 17deg. 0.; they were not, however, abolished. Reflex movements were obtained, even when the temperature sank to 15deg. or 14deg. C; and the observers believe that the excitability of the nervous system , disappeared not directly on account of the cold, but probably from arrest of the circulation. Spontaneous movements disappear before the reflex acts. The reflex from the cornea went before those from the lower limb 3. At 16deg. 0. the reflexes_ were remarkably slow, and like those in animals with a cold circulation. Sensibility to pain was not abolished even at the temperature of 16deg. 0. Cold gradually slowed the cardiac action. The form of the contraction at 17deg. 0. was like that of the heart of the tortoise. Systole commenced at the auricles, and by a slow vermionlar movement passed on to the ventricles. Even although death had been apparent for half an hour, the animal could be restored to life; so that- vitality can be recalled half an hour after the cessation of respiration and circulation. When the temperature was 19deg. 0., it took more than ten* minutes to asphyxiate the rabbit by blocking the trachea. We may conclude from this that tissue metabolism i 3 correspondingly slow. The same animal waii suffocated in four minutes at a temperature of 32deg. C. MM. Richet and Rondeau commented on the similarity between the vital processes of hibernating animals and those of rabbits thus experimented upon, in which a condition, so to speak, of artificial hibernation may be induced. — Lancet.