ZOOLOGY. 263 



Pavy was one dependent on chemical principles. The existence of 

 acidity was an absolutely essential condition for the accomplishment of 

 the act of digestion. Now, the walls of the stomach being permeated 

 so freely as they are during life by a current of alkaline blood, would 

 render it impossible that their digestive solution could occur. After 

 death, however, the blood being stagnant, there would not be the 

 resistance to the penetration of the digestive menstruum with the 

 retention of its acid properties that existed during the occurrence of 

 a circulation, and thus the stomach became attacked when death took 

 place during the digestive process, notwithstanding it had previously 

 been maintained in so perfect a state of security. Dr. Pavy, in ad- 

 vocating this view, brought forward experiments which showed that 

 digestion of the stomach might be made to take place during life. 

 Whenever the circumstances were such that an acid liquid in the stom- 

 ach could retain its acid properties whilst tending to permeate the 

 walls of the organ, gastric solution was observed. The question of 

 result resolved itself into degree of power between acidity within the 

 stomach and alkalinity around. It did not appear that the digestion 

 of living frogs' legs and the extremity of a living rabbit's ear intro- 

 duced through a fistulous opening into the stomach offered any valid 

 objection to his view. In the case of the frogs' legs, it might be fairly 

 taken that the amount of blood possessed by the animal would be in- 

 adequate to furnish the required means of resistance. In the case of 

 the rabbit's ear, the vascularity of it being so much less than that of 

 the walls of the stomach, there was nothing unreasonable in conceiving 

 that whilst the one received, the other might fail to receive protection 

 from the circulating current, on account of the disparity of power that 

 must belong to the two. 



THE BEATING OF THE HEART. 



About ten years ago, M. A. Bernard discovered a fact of very high 

 importance, - - the influence of certain nerves on the local circulation. 

 In his first researches, this eminent physiologist demonstrated that the 

 great sympathetic nerve was connected with the contractility of the 

 arterial terminations ; and further, the existence of nervous filaments 

 antagonistic to the preceding, which appeared to regulate the relaxa- 

 tion of the vessels. These experiments, repeated by all modern physi- 

 ologists, have been extended to other nerves, and show that the circu- 

 lation of the blood is accelerated or retarded by nervous influences in 

 a manner which was formerly only vaguely suspected. M. Marcy has 

 recently studied the subject in relation to the beating of the heart, 

 and its connection with muscular exercise, fever, and the violent emo- 

 tions of anger, fear, joy, &c., all of which exercise a direct action on 

 the peripheric circulation. He does not consider variation in the beat- 

 ing of the heart to be due to any change in the activity of the heart 

 alone. Without delivering himself to any hypothesis on the subject, 

 he says that it is certain that changes in the general circulation take 

 place under the influence of moral emotions, the face reddens, or pales, 

 etc. These changes must entail variations in the frequency of the 

 beatings of the heart, so that the power which moderates or accelerates 

 the contractions of the heart, he thinks, can be no other than the con- 

 tractility of the vessels of the whole body by nervous agency. 



