CH. XXIV.] ASPHYXIA 371 



direct obstruction of the trachea or other part of the respiratory 

 passages, or by introducing instead of ordinary air a gas devoid of 

 oxygen, or by interference with the due interchange of gases between 

 the air and the blood. 



The symptoms of asphyxia may be roughly divided into three 

 stages: (1) the stage of exaggerated breathing; (2) the stage of con- 

 vulsions ; (3) the stage of exhaustion. 



In the first stage the breathing becomes more rapid, and at the 

 same time deeper than usual, inspiration at first being especially 

 exaggerated and prolonged. The muscles of extraordinary inspiration 

 are called into action, and the effort to respire is laboured and painful. 

 This is soon followed by a similar increase in the expiratory efforts, 

 which become excessively prolonged, being aided by all the muscles 

 of extraordinary expiration. During this stage, which lasts a vary- 

 ing time from a minute upwards, according as the deprivation of 

 oxygen is sudden or gradual, the lips become blue, the eyes are 

 prominent, and the expression intensely anxious. The prolonged 

 respirations are accompanied by a distinctly audible sound; the 

 muscles attached to the chest stand out as distinct cords. This stage 

 includes the two conditions hyperpncea (excessive breathing) and 

 dyspnoea (difficult breathing), which follows later. It is due to the 

 increasingly powerful stimulation of the respiratory centre by the 

 increasingly venous blood. 



In the second stage, which is not marked by any distinct line of 

 demarcation from the first, the violent expiratory efforts become 

 convulsive, and then give way, in men and other warm-blooded 

 animals, to general convulsions, which arise from the further stimula- 

 tion of the centres in brain and cord by venous blood. Spasms of 

 the muscles of the body in general occur, and not of the respiratory 

 muscles only. The convulsive stage is a short one, and lasts less 

 than a minute. 



The third stage, or stage of exhaustion. In it the respirations all 

 but cease, the spasms give way to flaccidity of the muscles, there is 

 insensibility, the conjunctivas are insensitive and the pupils are 

 widely dilated. Every now and then a prolonged sighing inspiration 

 takes place, at longer and longer intervals, until breathing ceases 

 altogether, and death ensues. During this stage the pulse is scarcely 

 to be felt, but the heart may beat for some seconds after the respira- 

 tion has stopped. The condition is due to the gradual paralysis of 

 the centres by the prolonged action of the venous blood. This stage 

 may last three minutes and upwards. 



After death from asphyxia it is found in the great majority of 

 cases that the right side of the heart, the pulmonary arteries, and 

 the systemic veins are gorged with dark, almost black, blood, and 

 the left side of the heart, the pulmonary veins, and the arteries are 



