452 DIGESTION. 



zymogens, besides extractive bodies, leucine, purine bases, and mineral 

 substances. 



The occurrence of a mucinogen has not been proved. On the complete removal 

 of all mucin E. HOLMGREN l found no mucinogen in the submaxillary gland of 

 the ox, but a mucin-like gluconucleoproteid. 



The saliva is a mixture of the secretion of the above-mentioned groups 

 of glands; therefore it is proper that a study be made of each of the dif- 

 ferent secretions by itself and then of the mixed saliva. 



The submaxillary saliva in man may be easily collected by intro- 

 ducing a canula through the papillary opening into Wharton's duct. 



The submaxiliary saliva has not always the same composition or 

 properties; this depends essentially, as shown by experiments on animals, 

 upon the conditions under which the secretion takes place. That is to 

 say, the secretion is partly dependent on the cerebral system, through 

 the facial fibers in the chorda tympani, and partly on the sympathetic 

 nervous system, through the fibers entering the vessels in the gland. In 

 consequence of this dependence the two distinct varieties of submaxillary 

 secretion are distinguished as chorda- and sympathetic saliva. A third 

 kind of saliva, the so-called paralytic saliva, is secreted after poisoning 

 with curare or after the severing of the glandular nerves. 



The difference between chorda- and sympathetic saliva (in dogs) 

 consists chiefly in their quantitative constitution; the less abundant 

 sympathetic saliva is more viscous and richer in solids, especially in 

 mucin, than the more abundant chorda-saliva. The specific gravity of 

 the chorda-saliva of the dog is 1.0039-1.0056, and contains 12-14 p. m. 

 solids (EcKHARD 2 ). The sympathetic has a specific gravity of 1.0075-1.018, 

 with 16-28 p. m. solids. The freezing-point of the chorda-saliva obtained 

 from dogs on electric stimulation varies, according to NoLF, 3 between 

 A =-0.193 and -0.396, with a content of 3.3-6.5 p. m. salts and 4.1- 

 11.5 p. m. organic substances. The osmotic pressure is on an average a 

 little higher than one-half the osmotic pressure of the blood-serum. The 

 spontaneously secreted submaxillary saliva is ordinarily somewhat diluted. 

 On changing the 'osmotic pressure of the blood the osmotic pressure 

 of the saliva, according to JAPPELLI, 4 changes in the same direction. 

 According to DEMOOR, LOCKE'S solution with some dog serum is well 

 suited by transfusion to keep the submaxillary gland of the dog in 

 activity, while ox serum is unsuited. 5 The gases of the chorda-saliva 



1 Upsala Lakaref. Forh. (N. F.), 2; also Maly's Jahresber., 27. 



2 Cited from Kuhne's Lehrb. d. physiol. Chem., 7. 



3 See Maly's Jahresber., 31, 494. 



4 Jappelli, ibid., 48 and 51. 



5 Arch, intern, de Physiol., 10 (1911). 



