852 SPECIAL PHYSIOLOGY. 



portion, they are still quickly destroyed by asphyxia. It has been 

 found, moreover, that a diminution in the proportion of oxygen, in- 

 creases the poisonous effects of the carbonic acid; where the quantity 

 of oxygen is reduced to 16 or 10J per cent., death speedily ensues, 

 even though the carbonic acid is constantly being removed ; but if the 

 oxygen be maintained at its ordinary proportion of 21 per cent., the 

 ill effects of carbonic acid are not manifested more rapidly, even though 

 as much as 20 per cent, of that gas be present in the respired air. 

 A still more positive proof of the directly poisonous influence of car- 

 bonic acid, is furnished by the following singular experiment. One 

 bronchus of a tortoise was tied, and the animal lived apparently without 

 inconvenience ; the respiration, accomplished by one lung, being tem- 

 porarily sufficient. But if, by special arrangements, ordinary air was 

 allowed to enter one lung, and carbonic acid the other, through their 

 respective bronchi, the animal soon died, the introduction of carbonic 

 acid into the system being the sole difference in the two conditions. 

 This experiment also proves that carbonic acid may, in certain condi- 

 tions, not only not escape from the lungs, but may actually be absorbed 

 by them. (Rolando.) 



Suspended Respiration and Animation. 



The length of time which different animals, or Man, can survive 

 without respiration, varies, according to many conditions, chiefly ref- 

 erable to the relative degree of activity of the animal functions in any 

 given case, but sometimes also to special provisions. The more active 

 the nutritive and respiratory processes, and the greater the development 

 of heat, the sooner does death by suffocation ensue. Thus, cold-blooded 

 animals, with the feebler activity of all their functions, have less need 

 for air than warm-blooded animals, the water-newt, e. g., frequently 

 remaining, even in its active summer life, a quarter of an hour or more 

 under water; whilst frogs and lizards have been kept, in experiments, 

 for years without food, inclosed in porous stones, or buried in earth ; 

 but when they are hermetically inclosed, they sooner or later die. 

 Warm-blooded animals and Man, on the other hand, are rapidly as- 

 phyxiated. Hibernating Mammalia are able to live, in their peculiar 

 torpid condition, with a supply of air so defective, that they would 

 die asphyxiated in it, during their active summer condition. Newly- 

 born animals, being less dependent on the perfect state of respiration, 

 survive submersion for much longer periods, especially when their tem- 

 perature is low ; rabbits, under such circumstances, having survived 

 as long as 26 minutes, and puppies even 50 minutes; young guinea- 

 pigs, however, do not seem to possess this immunity. Even full-grown 

 animals resist the injurious effects of submersion in water, for a longer 

 time than usual, when their temperature has been previously reduced 

 as low as 64, but not lower. (Brown Sequard.) Again, it has been 

 observed, that full-grown warm-blooded animals die sooner from drown- 

 ing, than from simple apncea caused by immersion in nitrogen or hy- 

 drogen, by choking, or by strangulation, the more rapid fatal result in 

 drowning, being due, not only to the deprivation of air, but to the 



