378 ASPHYXIA. [BOOK n. 



The phenomena of slow asphyxia, where the supply of air is 

 gradually diminished, are fundamentally the same as those result- 

 ing from a sudden and total deprivation. The same stages are 

 seen, but their development takes place more slowly. 



The circulation in Asphyxia. If the carotid or other artery 

 of an animal be connected with a manometer during the develop- 

 ment of the asphyxia just described, the following facts may be 

 observed. During the first and second stages the blood-pressure 

 rises rapidly, attaining a height far above the normal. During the 

 third stage it falls even more rapidly, repassing the normal and 

 becoming nil as death ensues. The respiratory undulations of the 

 pressure-curve are abrupt and somewhat irregular, the inspiratory 

 movements being accompanied by a fall of pressure. When the 

 animal has been previously placed under urari, so that the respira- 

 tory impulses cannot manifest themselves by any muscular move- 

 ments, the rise of the pressure curve, as we have already said, is at 

 first steady and unbroken, but after a variable period Traube's 

 curves make their appearance. As during the third stage the 

 pressure sinks, these undulations pass away. 



The heart-beats are at first somewhat quickened, but speedily 

 become slow, while at the same time they acquire great force ; so 

 that the pulse-curves on the tracing are exceedingly bold and 

 striking, Fig. 61. Even while the blood-pressure is sinking, the 

 pulse-curves still maintain somewhat these characters; and the 

 heart continues to beat for some seconds after the respiratory 

 movements have ceased, the strokes at last rapidly failing in 

 frequency and strength. 



If the chest of an animal be opened under artificial respiration, 

 and asphyxia brought on by cessation of the respiration, it will be 

 seen that the heart during the second and third stages becomes 

 completely gorged with venous blood, all the cavities as well as 

 the large veins being distended to the utmost. If the heart be 

 watched to the close of the events, it will be seen that the feebler 

 strokes which come on towards the end of the third stage are quite 

 unable to empty its cavities ; and when the last beat has passed 

 away its parts are still choked with blood. The veins spirt out 

 when pricked : and it may frequently be observed that the beats 

 recommence when the over-distension of the heart's cavities is 

 relieved by puncture of the great vessels. When rigor mortis 

 sets in after death by asphyxia, the left side of the heart is more 

 or less emptied of its contents ; but not so the right side. Hence 

 in an ordinary post-mortem examination in cases of death by 

 asphyxia, while the left side is found comparatively empty, the 

 right appears gorged. 



These various phenomena of asphyxia are probably brought 

 about in the following way. 



The increasingly venous character of the blood augments the 



