RESEARCHES ON CHLOROFORM ANESTHESIA 645 



between the amount of chloroform present in the blood and 

 what is found at the lethal point is very minute. The state is 

 far from one of safety, and the animal may suddenly die at any 

 moment should any disturbing factors come into play. The 

 whole of this period is a danger period. In the experiments 

 quoted the percentage of inspired chloroform was maintained 

 constant, but it is evident that the contention of those anaes- 

 thetists who have insisted that after anaesthesia has been 

 established this can be and should be maintained with a much 

 smaller amount of chloroform vapour, rests upon a sound basis. 

 Space does not allow of more than a reference to the heart 

 failure which may occur in chloroform narcosis. An inhibition 

 of this organ to such an extent that no blood can be driven 

 through its chambers, though the heart is still beating, may 

 occur at the first danger point of anaesthesia. Particularly 

 valuable work in connection with this has been carried out by 

 Embley, 1 Leonard Hill, 2 and by Brodie and Russell. 3 Studied 

 from the point of view of a reflex action, the last observers 

 have shown that a very close relationship exists between the 

 respiratory tract and those nerve-centres of the brain which 

 control the heart-beat, the respiratory movements, and the bore 

 of the small arteries in the body. The most sensitive surface 

 which, when stimulated, reflexly affect these centres is that of 

 the lining of the nose, next the mucous lining of the larynx, 

 and then the surface of the lungs, which are powerfully 

 stimulated by vapours of chloroform, formaldehyde, and 

 bromine. When the internal surfaces of the trachea and 

 bronchi are irritated no reflex of the type just described 

 can be evoked. Stopping of the heart alone is very easily 

 brought about as a reflex action by stimulating the pulmonary 

 branches of the vagus. The experiments of Embley have 

 shown that for dogs the first danger point, cardiac inhibition, 

 and consequent slowing of the respirations, can be entirely set 

 aside by removal of the heart from the influence of the centres 

 in the brain by cutting the two vagi nerves along which the 

 impulses which check or arrest the heart normally pass. The 

 effect of atropin, which cuts out the inhibitory influence of 

 the vagus upon the heart, has been re-investigated by Schafer 



1 British Medical Journal, April 5, 12, and 19, 1902. 



2 Ibid., April 17, 1897, and December 1900. 



3 Journal oj Physiology, xxvi. 1900. 



