PANCREAS 33 



known as "hormones" Gastrin is absorbed and carried by 

 the blood to the gastric gland cells, thus exciting them to the 

 formation of their secretory product. 



To a certain extent the character of the secretion, as, for 

 instance, in acidity and digestive power, depends upon the 

 character of the food, but this effect is not a specific reaction. 

 For the quantity of the psychical secretion may in the first 

 instance depend upon the relish with which the animal eats 

 the food. The psychical secretion acting upon different kinds 

 of foods may liberate different products, which, determining 

 the quantity of the gastric hormone formed will determine 

 the amount of the secondary secretion. 



Pancreas. The cells of the pancreas are mainly of the 

 albuminous type, in addition to which irregular masses of 

 cells (bodies of Langerhans) are to be found. The latter are 

 clear and small, with readily stainable nuclei. The others 

 show a granular, well-defined, non-stainable zone toward the 

 lumen. During activity the cell boundaries become more 

 distinct and the granular zone becomes narrower. Stimula- 

 tion of the medulla increases the flow of the pancreatic juice 

 and changes its organic constituents, so that a centre in the 

 medulla is surmised. The nerve fibers supplying the pancreas 

 are comparable to those of the salivary glands in that they 

 are of two varieties bulbar autonomies and sympathetic 

 autonomies. The former run in the vagus, stimulation of 

 which, however, often fails to produce a secretion, since the 

 pancreas is very sensitive to changes in its blood supply. 

 Changes in blood supply are due to the fact that the tenth 

 nerve contains vasoconstrictors and cardio-inhibitory fibers. 

 This experimental difficulty is overcome by cutting the vagus 

 three or four days previously and then using slow stimula- 

 tions of one per second. A secretion then follows because the 

 secretory fibers respond to the stimulus while the cardio- 

 inhibitory fibers have degenerated and the vasoconstrictor 

 fibers are not affected by this kind of a stimulus. Having 

 established a pancreatic fistula, it may be seen that the secre- 

 tion appears in two or three minutes and continues for some 

 time after cessation of the stimulus. 



The presence of inhibitory fibers to the pancreas can be 

 established with ease. They exist both in the vagi and sympa- 

 3 



