CHEMICAL MECHANISMS OF SECRETION 295 



and discharged into the blood-stream, whence it reaches the gastric 

 secreting cells. 



The earlier experiments of Pawlow upon those substances 

 which excite gastric secretion on introduction into the stomach 

 are of interest in the light of these later experiments on intra- 

 venous injection. Thus introduction of water into the stomach, 

 even after section of both vagi, always gave rise to a secretion, 

 although not a very copious one; here there is a good deal cut 

 off from central control, as the vagi are clearly, from Pawlow's 

 other experiments, the most important efferent nerves for gastric 

 secretion, and it would be most interesting to know if this secretion 

 on the introduction of water also occurred after more profound 

 interference with the central nervous system connections e.g., if 

 it still took place after destruction of the spinal cord and extirpa- 

 tion of the solar plexus. 



Alkaline solutions, such as sodium bicarbonate, were found 

 by Pawlow to exercise an inhibitory effect upon gastric secretion. 

 Fresh meat and meat extracts were the most powerful excitants, 

 and research is still required to test whether this action is nervous 

 or chemical in origin. Starch and fat were found by Pawlow not 

 to excite secretion on direct introduction without psychical stimula- 

 tion. Bread and solution of egg- albumin also appeared to be non- 

 excitants, but the fluid digestive products from the stomach of 

 another dog which had eaten egg- albumin, when introduced without 

 psychical effect directly into the main stomach, gave a stronger 

 and more constant effect than a like quantity of water. 



The above experiments upon the effects of chemical stimulants 

 formed in the cells of the body itself upon the activity of the secret- 

 ing cells of pancreas and stomach open up to physiological research 

 a Held of great importance, and one with practical bearing for 

 medicine and organotherapy. Doubtless similar actions occur 

 elsewhere in the body which will in the future be brought to light. 

 Bayliss and Starling in their paper briefly draw attention to what 

 they term the chemical sympathies between uterus and mammary 

 gland, and to the modifications in the composition of the pancreatic 

 juice accompanying long-continued change in the diet such, for 

 example, as the production of a lactase as the result of milk feed- 

 ing and call attention to the advisability of a renewed investiga- 

 tion of these facts from the point of view of the production in 

 such cases of bodies allied to secretin. There is no doubt that 



