PHENOMENA OF ASPHYXIA. 851 



for the circulation in the transparent parts of animals may be arrested 

 by subjecting the capillaries to the action of carbonic acid ; moreover, 

 as the red corpuscles of the blood undergo enlargement when acted 

 upon by this gas, it has been supposed that these bodies may then ob- 

 struct the capillaries mechanically. (Wharton Jones.) It has also been 

 suggested that there exist, in the healthy state, certain local attrac- 

 tions and repulsions between the walls of the pulmonary capillaries 

 and the currents of the non-aerated and the aerated blood respectively, 

 connected with the respiratory interchanges of the carbonic acid and 

 oxygen, which are essential to the onward movement of the blood- 

 current. 



In the slower forms of asphyxia, indicated by the more gradually 

 developed cerebral symptoms, the stagnation of the blood in the pul- 

 monary capillaries is preceded by a simple retardation of the blood- 

 current in them ; but the entire blood is defectively aerated. Hence 

 this fluid, owing to its abnormal condition, passes imperfectly through 

 the systemic capillaries; the arteries and the left ventricle become 

 somewhat distended; and the heart for a time beats more powerfully 

 and more frequently, as if to overcome this resistance. But the ac- 

 tivity of the nervous centres and muscular system is soon diminished, 

 in proportion as the blood becomes less and less aerated ; at length, 

 both are completely paralyzed, the senses fail, consciousness is lost, 

 the respiratory nervous centres lose their power, respiration becomes 

 labored and much interrupted, general convulsions ensue, and respira- 

 tion ceases. The contractile power of the heart itself, becoming dimin- 

 ished, it beats more slowly, and at length ceases to contract. The 

 left ventricle not only no longer receives its appropriate stimulating 

 blood, but even loses its power of rhythmic contraction, owing to the 

 poisoning of the blood in the nutrient vessels of the heart and its ner- 

 vous ganglia ; whilst the cessation of the action of the right ventricle 

 is chiefly the result of over-distension, for venous blood is its proper 

 stimulus, and the contractility of that side of the heart is retained, for 

 more or less time, after it has ceased to beat spontaneously. If, indeed, 

 the state of over-distension be relieved by puncturing the right auricle 

 or the great veins, the right ventricle will again begin to contract ; 

 whilst the left ventricle may be once more excited by duly arterialized 

 blood. By some, it has been supposed that the obstruction to the pul- 

 monary capillary circulation, is due to the mechanical non-expansion 

 of the lungs, but it also occurs in asphyxia produced in animals made 

 to respire nitrogen, in which case, the lungs are not contracted. More- 

 over, the vascular pulmonary obstruction which is caused by asphyxia, 

 is relieved by the inhalation of oxygen, very rapidly, as compared with 

 the gradual dilatation of the arterial system, when any mechanical 

 obstruction to the circulation of the blood in them> has to be removed. 

 The question has arisen, whether in asphyxia from the inhalation of 

 carbonic acid, the result is due to the diminished supply of oxygen, or 

 to a directly poisonous effect of the carbonic acid itself. The latter 

 conclusion is supported by the fact that when animals are made to 

 breathe an atmosphere consisting of carbonic acid, mixed with oxygen, 

 in the same proportion as exists in air, or even in much greater pro- 



