THE RESPIRATORY SYSTEM. 401 



and in any case the whole venous system, including the right 

 heart, tends to hecome engorged from these several causes act- 

 ing together. The heart gives up the struggle, unahle to main- 

 tain it, but not so long as it can beat in any part. 



The share which the elasticity of the arteries takes in 

 forcing on the blood when the heart ceases, and the contraction 

 of the muscular coat of these vessels, especially the smaller, 

 must not be left out of the account in explaining the phenom- 

 ena of asphyxia and the post-mortem appearances. 



Pathological. — ^The importance of being practically as well 

 as theoretically acquainted with the facts of asphyxia is very 

 great. 



The appearance of the heart and venous system gives une- 

 quivocal evidence as to the mode of death in any case of as- 

 phyxia; and the contrast between the heart of an animal bled 

 to death, or that has died of a lingering disease, and one 

 drowned, hanged, or otherwise asphyxiated, is extreme. 



We strongly recommend the student to asphyxiate some 

 small mammal placed under the influence of an anaesthetic, 

 and to note the phenomena, preferably with the chest opened; 

 and to follow up these observations by others after the onset of 

 rigor mortis. 



PECULIAR RESPIRATORY MOVEMENTS. 



Though at first sight these seem so different, and are so as 

 regards acts of expression, yet from the respiratory point of 

 view they resemble each other closely; they are all reiiex, and, 

 of course, involuntary. Many of them have a common pur- 

 pose, either the better to ventilate the lungs, to clear them of 

 foreign bodies, or to prevent their ingress. 



Coughing:, in which such a purpose is evident, is made up of 

 several expiratory efforts preceded by an inspiratory act. The 

 afferent nerve is usually the vagus or laryngeal, but may be one 

 or more of several others. 



The glottis presents characteristic appearances, being closed 

 and then opened suddenly, the mouth being kept open. 



Coughing is often induced in attempting to examine the ear 

 with instruments. (Keflex act). 



Laughing is very similar to the last, so far as the behavior 

 of the glottis is concerned, though it usually acts more rapidly, 

 of course. Several expirations follow a deep inspiration. 

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