SECRETIONS 95 



The centre of the secretory nerves is situated in the 

 medulla oblongata. 



For some time after the section of the secretory nerves the 

 gland secretes continuously (paralytic secretion) till it finally dies 

 and degenerates. The cause of this paralytic secretion is still in 

 the dark. 



The pressure of the secretion is measured by placing a canula 

 in the duct of the gland and connecting this with a manometer. 

 In the submaxillary of the dog the pressure during chorda stimula- 

 tion may be above 200 mm Hg, this being 100 mm more than the 

 blood pressure in the blood vessels of the gland. 



The secretion of the salivary glands is said to be warmer than 

 that of the blood carried to the gland. Hence heat is produced 

 during salivary secretion. 



The active gland shows certain electrical phenomena, the mean- 

 ing of which is not yet understood. 



Upon nervous stimulation, secretion can go on in a bled 

 animal, in which case the gland is no longer supplied with 

 blood. 



3. GASTRIC SECRETION 



I. Composition of gastric juice. Gastric juice, the secre- 

 tion of the gastric glands, is a clear, transparent or slightly 

 yellowish fluid, having an acid reaction and a specific gravity 

 of 1.003-1.006. It contains 0.29-0.60$ solids which include 

 o. 10-0.17^ ash. 



Its characteristic constituents are: 



(a) Free hydrochloric acid, in man o. 2% ; in dogs a little 

 more. 



The gastric juice gives the following tests for free hydrochloric 

 acid: To gastric juice add Giinzburg's reagent (2 g phloroglucin, 

 i g. vanillin in 30 g absolute alcohol) and evaporate. This gives 

 a red color. Gastric juice imparts a blue color to methyl-violet 

 and congo-red. 



(b) Pepsin, a ferment which in an acid solution digests 

 proteids and gelatin. According to its composition, it is a 

 proteid-like body. The antecedent of pepsin in the gastric 

 glands is the pepsinogen, a substance which can be extracted 



