330 PULMONARY MUCOUS TISSUE. 



in different animals. Not that carbonic acid is a poison, but 

 only that the excess of this gas (or its too great pressure) in 

 the air, hinders the egress of that which is in the blood ; the 

 blood is thus prevented from collecting the gas evolved from 

 the combustion of the tissues, and the respiration of the latter 

 becomes impeded. 



In the case of asphyxia in a confined atmosphere, both the 

 causes which we have mentioned are found to exist ; diminu- 

 tion of oxygen and increase of carbonic acid. Both occur, 

 but in different and varying proportions. By means of 

 numerous experiments, which we have not space to describe, 

 Paul Bert has reached the conclusion that death in a con- 

 fined air is caused, in warm-blooded animals, by the want of 

 oxygen, and, in cold-blooded animals, by an excess of car- 

 bonic acid. 1 



In a natural death, whatever be the cause, the blood, 

 arterial as well as venous, loses all its oxygen. This is why 

 Paul Bert pronounces the somewhat paradoxical opinion that 

 " death is always owing to asphyxia." 



b. The type of asphyxia by intoxication is asphyxia by 

 carbonic oxide ; this gas constitutes the poisonous agent in 

 cases of asphyxia from the fumes of charcoal (Leblanc). Here, 

 the red globule is first affected ; we have already seen, in 

 studying the spectroscopic features of the blood (p. 119), 

 that the carbonic oxide takes the place of oxygen in the 

 hemoglobin, and we can easily understand that this oxy- 

 carbonized hemoglobin is no longer fit to keep up the 

 combustion of the tissues; 2 thus in asphyxia, by means of 

 carbonic oxide, the temperature is lowered (01. Bernard). 

 We find, in short, that this asphyxia consists in the depriva- 



1 See Paul Bert, " Lemons sur la Respiration." Legons 27 

 and 28. 



2 This intoxication is effected with remarkable rapidity. Gre- 

 hant's experiments on dogs show that in an animal breathing air 

 containing one-tenth of carbonic oxide, the arterial blood, between 

 the tenth and the twenty-fifth second, contains 4 per cent of car- 

 bonic oxide, and only 14 per ceut of oxygen; and that, in a space 

 of time varying from one minute and fifteen seconds to one minute 

 and thirty seconds, a large proportion (18.4 per cent) of carbonic 

 oxide appears in the blood, while the quantity of oxygen diminishes 

 until it is reduced to 4 per cent. We may therefore conclude, with 

 Grehant, that, from the first moment that a man enters an atmos- 

 phere which is heavily laden with carbonic oxide, the poison of this 

 gas is absorbed by the arterial blood, or, in other words, almost 

 instantly takes the place of oxygen in the globule, rendering it 

 incapable of absorbing oxygen. 



