CHEMICAL MECHANISMS OF SECRETION 



ordinary type in only having simple glands as in the pyloric, 

 extracts of the cardiac region in general have the same efficiency 

 in promoting secretion as do pyloric." 



The media most powerful in calling forth secretion in these 

 experiments are hence those containing the products of advanced 

 salivary digestion, or of peptic digestion, viz. glucose, maltose 

 and commercial peptone, and the region from which active pre- 

 parations can be prepared being the pyloric mucous membrane, 

 which also is the region in which any slight absorption in the 

 stomach occurs, the indication of the experiments is that the 

 precursor of the active gastrin is formed in the pyloric mucosa, 

 and is activated by the absorption of these digestive products, 

 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 found to be the most powerful 

 excitants, and research is 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 stimulation. Bread and solution of egg-albumin also 

 were found 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 



