376 ASPHYXIA. [BOOK n. 



assist in expiration is in turn brought into play; and at last almost 

 all the muscles of the body are involved in the struggle. The 

 orderly expiratory movements culminate in expiratory convulsions, 

 the order and sequence of which are obscured by their violence and 

 extent. That these convulsions, through which dyspnoea merges 

 into asphyxia, are due to a stimulation of the medulla oblongata 

 by the venous blood, is proved by the fact that they fail to make 

 their appearance when the spinal cord has been previously divided 

 below the medulla, though they still occur after those portions of 

 the brain which lie above the medulla have been removed. It is 

 usual to speak of a 'convulsive centre' in the medulla, the stimu- 

 lation of which gives rise to these convulsions ; but if we accept 

 the existence of such a centre we must at the same time admit 

 that it is connected by the closest ties with the normal expiratory 

 division of the respiratory centre, since every intervening step 

 may be observed between a simple slight expiratory movement 

 of normal respiration and the most violent convulsion of asphyxia. 

 An additional proof that these convulsions are carried out by the 

 agency of the medulla is afforded by the fact that convulsions of 

 a wholly similar character are witnessed when the supply of 

 blood to the medulla is suddenly cut off by ligaturing the blood- 

 vessels of the head. In this case the nervous centres, being no 

 longer furnished with fresh blood, become rapidly asphyxiated 

 through lack of oxygen, and expiratory convulsions quite similar to 

 those of ordinary asphyxia, and preceded like them by a passing 

 phase of dyspnoea, make their appearance. Similar 'anaemic' con- 

 vulsions are seen after a sudden and large loss of blood from the 

 body at large, the medulla being similarly stimulated by the lack of 

 arterial blood. 



Such violent efforts speedily exhaust the nervous system ; and 

 the convulsions after being maintained for a brief period suddenly 

 cease and are followed by a period of calm. The calm is one of 

 exhaustion; the pupils, dilated to the utmost, are unaffected by 

 light ; touching the cornea calls forth no movement of the eyelids, 

 and indeed no reflex actions can anywhere be produced by the 

 stimulation of sentient surfaces. All expiratory active movements 

 have ceased ; the muscles of the body are flaccid and quiet ; and 

 though from time to time the respiratory centre gathers sufficient 

 energy to develope respiratory movements, these resemble those of 

 quiet normal breathing, in being, as far as muscular actions are 

 concerned, almost entirely inspiratory. They occur at long intervals, 

 like those after section of the vagi; and like them are deep 

 and slow. The exhausted respiratory centre takes some time to 

 develope an inspiratory explosion; but the impulse when it is 

 generated is proportionately strong. It seems as if the resistance 

 which had in each case to be overcome was considerable, and 

 the effort in consequence, when successful, productive of a large 

 effect. 



