and the Action of Cold upon Animal'}. 223 



The carotids having been laid bare in a lethargic lerot, and 

 by an operation which might have been supposed to be painful, 

 but which the animal scarcely felt, I found that they did not 

 beat, even after the operation, more than nine or ten times in a 

 minute. Some time after, the animal tending more and more to 

 awake, and the respiration to recommence, they beat twenty, 

 then thirty, then forty-five, then a hundred, and lastly a hun- 

 dred and ten pulsations in the minute, when the respiration was 

 perfectly re-established. 



Having then subjected this lerot to the action of cold, I saw 

 its respiration gradually weaken, and its carotids beat at first 

 only a hundred, then sixty-five, then fifty, then forty-seven, 

 then thirty, then twenty, and, lastly, eight or nine pulsations 

 still in the minute, when the respiration again entirely ceased, 

 and the animal became perfectly torpid. 



It was thought curious to see if the artificial suspension of re- 

 spiration might not induce a result similar to that which lethargy 

 had just produced. Respiration was therefore artificially sus- 

 pended in a lerot, in its ordinary state. The blood of the caro- 

 tids presentlv became black, and the pulsations diminished in 

 number. In four minutes they were only thirty-two. Half an 

 hour later they ceased ; the heart alone beat eight or nine times 

 in the minute, which was precisely the number I found it to 

 beat in the former animal when in perfect torpidity. By sus- 

 pending the respiration, in this experiment, I had reproduced 

 the state of the circulation in the lethargic condition itself; for, 

 with the state of the circulation, that of the rest of the economy 

 always corresponds. 



Respiration was then successively suspended in different le- 

 I'Ots, more and more intensely torpified, and I observed the fol- 

 lowing results. In all of them, the circulation survived the re- 

 spiration a certain time ; in all of them, this time was so much 

 the longer the deeper the torpidity was, and the temperature 

 fitted for the lethargic stale. At length I succeeded, by alter- 

 nately interrupting and continuing the suspension of the respi- 

 ration, in rendering the animal lethargic, under degrees of cold 

 less than those which would have been requisite to produce that 

 effect were the respiration free. Every thing, therefore, shews 



q2 



