520 THE SALIVAR Y GLANDS. 



fibres to degenerate is not quite accurately known, Heidenhain states 

 that in the dog, stimulation of the chorda causes a secretion three to four 

 days after its section, and implies that later than this the nerve has no 

 effect. 1 In an experiment on the cat, 1 2 obtained a copious secretion by 

 stimulating the cut end of the chorda three days after section ; a secre- 

 tion too copious, it seemed to me, to be attributed to the nerve-cells 

 which sometimes occur in the region stimulated. But Bradford, 3 three 

 days after section of the chordo-lingual nerve near the pterygoid muscle, 

 obtained no secretion from stimulation of the nerve up to the point 

 where the chorda tympani leaves the lingual. In the dog he found no 

 effect five days after section, but no experiment was made at an earlier 

 date. It appears, then, that the time required for a loss of irritability 

 of the cut chorda tympani in the cat and dog lies somewhere between 

 three and five days. 



Notwithstanding the early loss of irritability of the chorda tympani 

 after section, stimulation of its nerve-strands near the gland will in the 

 cat still cause secretion. In this way I obtained a fairly rapid secretion 

 thirteen days after section of the nerve, and a slight secretion in another 

 experiment forty-two days after section of the nerve. And Bradford 

 obtained secretion from the chorda tympani in the cat up to eleven days 

 after section of the chordo-lingual. In his experiments he sometimes 

 obtained a secretion by stimulating the chorda immediately after it had 

 left the lingual nerve, but sometimes only when the electrodes were 

 shifted farther towards the gland. In the dog, five or more days after 

 section, he obtained no secretion by stimulating the chorda in any part 

 of its course. 



Vulpian 4 noticed in the dog, that a fortnight after section of the 

 chorda tympani, injection of extract of jaborandi into a vein gave rise to 

 a secretion, though less than normal. Extirpation of the superior 

 cervical ganglion at the time of section did not affect the result. In 

 the cat, I found that thirteen days after section of the chorda, venous 

 injection of a few mgrms. of pilocarpine caused a copious secretion, 

 and that forty-two days after section of the nerve, pilocarpine still caused 

 a secretion, though distinctly less than on the opposite side. 



These experiments, taken together with those already given on the 

 action of nicotine (cf. p. 515), and with our general knowledge of the 

 relation of visceral nerve-fibres to nerve-cells, show that, on section of 

 the chorda tympani, its nerve-fibres degenerate in three to five days up 

 to the peripheral nerve-cells. The nerve-cells are placed chiefly in the 

 gland itself more so in the dog than in the cat. And there can lie 

 little doubt that the variations observed as the result of stimulating the 

 peripheral portions of the chorda depend in the main upon variations in 

 the position of the peripheral ganglia. In some animals, postganglionic 

 fibres are stimulated when the electrodes are placed on the strands 

 outside the gland ; in other animals, this only occurs when the electrodes 

 are placed in the hilus. As the gland diminishes in size it naturally 

 gives a less copious secretion under the influence of pilocarpine. 



1 Heidenhain (Hermann's "Handbuch," 1880, Bd. vi. S. 88) states that, although there 

 was secretion, there was no increased flow of blood. 



2 Journ. PhysioL, Cambridge and London, 1885, vol. vi. p. 71. 



3 Ibid., 1888, vol. ix. p. 304. 



4 Compt. rend. Acad. d. sc., Paris, 1878, tome Ixxxvii. p. 350. Before this, Provost had 

 stated that muscarine causes secretion after degeneration of the chorda tympani ; cf. Arch, 

 de physiol. norm, etpath., Paris, 1874, p. 719, note. 



