188 RESPIRATION. 



trance of water into them. In proof of the correctness of this 

 explanation it was found that when two dogs of the same size, 

 one, however, having his windpipe plugged, the other not, were 

 submerged at the same moment, and taken out after being 

 under water for 2 minutes, the former recovered on removal 

 of the plug, the latter did not. It is probably to the entrance 

 of water into the lungs that the speedy death in drowning is 

 mainly due. The results of post-mortem examination strongly 

 support this view. On examining the lungs of animals de- 

 prived of air by plugging the trachea, they were found simply 

 congested ; but in the animals drowned, not only was the con- 

 gestion much more intense, accompanied with ecchymosed 

 points on the surface and in the substance of the lung, but the 

 air-tubes were completely choked up with a sanious foam, con- 

 sisting of blood, water, and mucus, churned up with the air in 

 the lungs by the respiratory efforts of the animal. The lung- 

 substance, too, appeared to be saturated and sodden with water, 

 which, stained slightly with blood, poured out at any point 

 where a section was made. The lung thus sodden with water 

 was heavy (though it floated), doughy, pitted on pressure, and 

 was incapable of collapsing. It is not difficult to understand 

 how, by such infarction of the tubes, air is debarred from reach- 

 ing the pulmonary cells : indeed the inability of the lungs to 

 collapse on opening the chest is a proof of the obstruction 

 which the froth occupying the air-tubes offers to the transit of 

 air. The entire dependence of the early fatal issue, in apnoea 

 by drowning, upon the open condition of the windpipe, and its 

 results, was also strikingly shown by 'the following experi- 

 ment. A strong dog had its windpipe plugged, and was then 

 .submerged in water for four minutes ; in three-quarters of a 

 minute after its release it began to breathe, and in four minutes 

 had fully recovered. This experiment was repeated with sim- 

 ilar results on other dogs. When the entrance of water into 

 the lungs, and its drawing up with the air into the bronchial 

 tubes by means of the respiratory efforts, were diminished, as 

 by rendering the animal insensible by chloroform previously 

 to immersion, and thus depriving it of the power of making 

 violent respiratory efforts, it was found that it could bear im- 

 mersion for a longer period without dying than when not thus 

 rendered insensible. Probably to a like diminution in the 

 respiratory efforts, may also be ascribed the greater length of 

 time persons have been found to bear submersion without 

 being killed, when in a state of intoxication, poisoning by nar- 

 cotics, or during insensibility from syncope. 



It is to the accumulation of carbonic acid in the blood, and 

 its conveyance into the organs, that we must, in the first place, 



