608 ASPHYXIA. [BOOK 11. 



repeated inspirations. The pauses become longer, and the in- 

 spiratory movements shallower. Each inspiration is accompanied 

 by the contraction of accessory muscles, .especially of the face, so 

 that each breath becomes more and more a prolonged gasp. The 

 inspiratory gasps spread into a convulsive stretching of the whole 

 body; and with extended limbs, and a straightened trunk, with the 

 head thrown back, the mouth widely open, the face drawn, and 

 the nostrils dilated, the last breath is taken in. 



Thus we are able to distinguish three stages in the phenomena 

 which result from a continued deficiency of air: (1) A stage of 

 dyspnoea, characterized by an increase of the respiratory move- 

 ments both of inspiration and expiration. (2) A convulsive stage, 

 characterized by the dominance of the expiratory efforts, and 

 culminating in general convulsions. (3) A stage of exhaustion, in 

 which lingering and long-drawn inspirations gradually die out. 

 When brought about by sudden occlusion of the trachea these 

 events run through their course in about 4 or 5 minutes in the 

 dog, and in about 3 or 4 minutes in the rabbit. The first stage 

 passes gradually into the second, convulsions appearing at the end 

 of the first minute. The transition from the second stage to the 

 third is somewhat abrupt, the convulsions suddenly ceasing early 

 in the second minute. The remaining time is occupied in the 

 third stage. 



The duration of asphyxia varies not only in different animals 

 but in the same animal under different circumstances. Newly 

 born and young animals need much longer immersion in water 

 before death by asphyxia occurs than do adults. Thus while in a 

 full-grown dog recovery from drowning is unusual after 1^ minutes, 

 a new-born puppy has been known to bear an immersion of as 

 much as 50 minutes. The cause of the difference lies in the fact 

 that in the quite young or rather just born animal the respiratory 

 changes of the tissues are much less active. These consume less 

 oxygen, and the general store of oxygen in the blood has a less 

 rapid demand made upon it. The respiratory activity of the 

 tissues may also be lessened by a deficiency in the circulation; 

 hence bodies in a state of syncope at the time when the depriva- 

 tion of oxygen begins can endure the loss for a much longer period 

 than can bodies in which the circulation is in full swing. There 

 being the same store of oxygen in the blood in each case, the 

 quicker circulation must of necessity bring about the speedier 

 exhaustion of the store. So also anaesthetics may diminish the 

 effects and delay the final Results ; large doses of anaesthetics may 

 prevent the exaggerated and convulsive movements. In many 

 cases of drowning, death is hastened by the entrance of water 

 into the lungs. 



By training, the respiratory centre may be accustomed to bear 

 a scanty supply of oxygen for a much longer time than usual 

 before dyspnoea sets in, as is seen in the case of divers. 



