. A text-book of comparative physiology for students and practitioners of comparative (veterinary) medicine . erioles of the gland become dilated ; the blood may passthrough with such rapidity that the venous blood may bebright red in color and there may be a venous pulse. 7. Stimu-lation of the medulla oblongata gives rise to a flow of saliva,which is not possible when the nerves of the gland, especiallythe chorda tympani, are divided; nor can a flow be then excitedby any sort of nervous stimulation, excepting that of the ter-minal branches of the nerves of the gland itself. 8. If the sym-pat
. A text-book of comparative physiology for students and practitioners of comparative (veterinary) medicine . erioles of the gland become dilated ; the blood may passthrough with such rapidity that the venous blood may bebright red in color and there may be a venous pulse. 7. Stimu-lation of the medulla oblongata gives rise to a flow of saliva,which is not possible when the nerves of the gland, especiallythe chorda tympani, are divided; nor can a flow be then excitedby any sort of nervous stimulation, excepting that of the ter-minal branches of the nerves of the gland itself. 8. If the sym-pathetic nerves of the gland be divided, there is no immediateflow of saliva, though there may be some dilatation of its ves- DIGESTION OF FOOD. 313 sels. 9. Stimulation of the terminal ends of the sympatheticand chorda nerves causes a flow of saliva, differing as to totalquantity and the amount of contained solids; hut the nervethat produces the more abundant watery secretion, or the re-verse, varies with the animal, e. g., in the cat chorda saliva is Part of brain above medulla Afferent nervesfrom tongue-. Fig. 256. -Diagram intended to indicate the nervous mechanism of salivary secretion. more viscid, in the dog less so; though in all animals as yetexamined it seems that the secretion as a result of stimulationof the chorda tympani nerve is the most abundant; and in the 314 COMPARATIVE PHYSIOLOGY. case of stimulation of the chorda the vessels of the gland aredilated, while in the case of the sympathetic they are con-stricted. 10. If atropin be injected into the blood, it is impos-sible to induce salivary secretion by any form of stimulation,though excitation of the chorda nerve still causes arterial dila-tation. Conclusions.—1. There is a center in the medulla presidingover salivary secretion. 2. The influence of this center is ren-dered effective through the chorda tympani nerve at all events,if not also by the sympathetic. 3. The chorda tympani nervecontains both secretory
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