512 British Association for the Advancement of Science. 



but not containing oxygen ; in which case it had been observed by 

 Broughton and others, that the stagnation of blood in the lungs, and 

 the distention of the right side of the heart, take place equally as 

 when the respiratory movements are suspended. But to this obser- 

 vation it might be objected, that the animals on which experiment had 

 been made had been allowed to remain in the azote until they became 

 insensible, and their respiration of course ceased, and had not been 

 examined until some minutes after their apparent death, and it might 

 be said, that the right side of the heart had become congested only 

 after the acts of respiration had ceased, and in consequence of their 

 cessation. 



In order to avoid this source of fallacy several rabbits were con- 

 fined in azote, only until their breathing became laboured, the re- 

 spirations generally less frequent, but much longer and fuller 

 than natural. They were then taken out and instantly struck on 

 the head with such force as to crush the brain and cerebellum, and 

 arrest the circulation as instantaneously as possible. This was always 

 attended with violent and general convulsion, but with no attempt 

 at respiration, sensation being apparently instantaneously suppressed. 

 When the body was opened immediately after the convulsion had 

 subsided, the right side of the heart was always found distended 

 with blood, and palpitating feebly ; the left side at rest and compa- 

 ratively empty : the quantity of blood obtained by puncturing and 

 pressing the right side and pulmonary artery was from 5 to 10 times 

 as much as could be obtained from the left side and aorta. When 

 a, rabbit previously breathing naturally was killed in the same man- 

 ner, the quantity of blood on the right side of the heart (apparently 

 accumulating there during the convulsions) was found to be greater 

 than on the left ; but the difference was decidedly less than when 

 it had been breathing azote ; and in one of these comparative trials 

 the blood in the left side was found to be sufficient to keep up a 

 feeble palpitation in that side, whereas in the animals that had 

 breathed azote the left side was always found quite at rest. 



It appears from these experiments that when oxygen is not ad- 

 mitted into the lungs in inspiration, even although the respiratory 

 movements continued further and more forcible than usual up to the 

 moment of death, the blood stagnates on the right side of the heart ; 

 and that the application of oxygen to the blood at the lungs is a 

 cause of acceleration of its movement through the lungs, indepen- 

 dently of any influence of the mechanical movements of respiration. 



If we further inquire, in what manner oxygen can give this sti- 

 mulus to the flowing blood through the lungs, it appears certain 

 that it cannot be by stimulating the small capillaries of the lungs 

 (the only vessels to which it is directly applied) to contraction, be- 

 cause even if it be granted that there are vessels capable of con- 

 tracting on irritation (which is very doubtful), the immediate effect 

 of stimulating any arteries capable of taking on such action has 

 always been observed to be a constriction permanent for some 

 length of time, and in consequence a retarded flow of the fluids 

 through them, as in the experiments of Wedmeyer. 



If, again, we suppose the effect of the oxygen on the minute ves- 



