PROPERTIES OF THE SALIVARY SECRETION. 



149 



rest, secreting little or no saliva, whilst the venous blood returning from them 

 is of a dark tint. If a drop of vinegar be now placed upon the tongue of 

 the animal, the arterial twigs supplying the gland immediately enlarge, the 

 rapidity of the current of blood is increased, the veins pulsate and convey 

 scarlet blood, the pressure of which on their inner surface is considerably 

 increased, and there is an abundant 1 discharge of limpid, highly alkaline 

 saliva, containing small quantities of albumen (Globulin) and mucin. (This 

 is termed chorda tympani saliva.} These conditions are brought about by 

 an action transmitted through the sensory branches of the fifth and glosso- 

 pharyngeal nerves to the Medulla oblongata, from which it is reflected through 

 excito-secretory nerves contained in the chorda tympani, and primarily de- 

 rived from the facial. If either of these latter nerves be cut, the current of 



FIG. 64. 



The Subraaxillary and Sublingual Glands of the dog, with the nerves and vessels in relation to the sub- 

 maxillary gland ; to show the mechanism of the secretion in this gland. 



N, submaxillary salivary gland ; o, sublingual, JM, Wharton's duct ; JL, duct of sublingual, each with 

 a canula tied into it ; T ss' lingual branch of the inferior maxillary division of the Fifth nerve; ss', 

 branches distributed to the mucous membrane of the mouth; F, facial nerve; c, chorda tympani ; a, 

 branch of the Facial distributed to the submaxillary gland after running for a short distance with the 

 lingual of the Fifth ; g, submaxillary sympathetic ganglion ; <?, superior cervical ganglion ; p, branch 

 from this ganglion to the submaxillary gland ; j, internal maxillary artery ; V, vidian nerve ; /, branch 

 of the lingual nerve ramifying in the buccal mucous membrane. 



blood becomes slower, its color in the veins black, the secretion of Saliva 

 diminishes, and vinegar placed on the tongue no longer excites the secretion ; 

 whilst, if their distal cut extremities be again irritated, all the former phe- 

 nomena recur. On the other hand, if the sympathetic branches proceeding 

 to these glands be directly irritated, the current of blood becomes very slow, 

 in consequence of the contraction of the vessels, its color in the veins very 

 dark, and the secretion of Saliva, whilst it diminishes in quantity, becomes 

 at the same time cloudy and remarkably viscous, contains more albumen 

 and mucin, and, according to Eckhard, a remarkable number of sarcode-like 

 bodies possessing the power of spontaneous movement. (This is termed sym- 

 pathetic saliva.) That the secretion does not wholly cease after section of the 

 chorda tympani, is believed by Bernard to be due to the reflex action of the 

 submaxillary ganglion, 2 but even when the sympathetic fibres are divided, it 



1 856 grains in one hour in a dog (Ludwig). 



2 Though this is rendered very doubtful by the experiments of Schiff, Le9ons sur 

 la Physiologic de la Digestion. Florence, 18G6. 



