492 THE SALIVARY GLANDS. 
is less copious than that obtained by placing acids in the mouth, and it 
is more copious on the side stimulated than on the opposite side. 
A special relation has also been said to exist between the state of 
the mucous membrane of the stomach and the secretion of saliva. Thus 
it has been said that a secretion of saliva is induced by the contact of 
various substances with the gastric mucous membrane. 1 This, however, 
is not satisfactorily proved. Braun 2 observed a dog, in which a gastric 
fistula had been established, and a cannula placed in Wharton's duct. 
No secretion of saliva was caused by introducing into the stomach, 
flesh, acetic acid, ether, nor by irritating the mucous membrane with, a 
sponge. 
Stimulation of the central end of the vagus has rather variable 
results on the submaxillary secretion of the dog. It usually causes 
secretion after a long latent period, and the secretion may continue for 
some time after the cessation of the stimulus. Oehl 3 obtained secretion 
although the stimulation caused no vomiting or arrest of respiration ; the 
secretion occurred from both glands, but was greater on the side stimu- 
lated. Buff, as a rule, only obtained secretion when there was some 
1 »( h 1 v movement. 
Bernard noticed that a flow of saliva may lie obtained by stimulating 
the sciatic 4 and various other sensory nerves ; it may, indeed, be obtained 
by stimulating any sensory nerve in the body. This reflex secretion is 
abolished by deep anaesthesia ; whether it ceases coincidently with the 
production of anaesthesia is, however, uncertain. According to Buff, 5 
the secretion does not occur in uncurarised animals, unless the stimulus 
produces also a reflex body movement. 
The gustatory reflex secretion is caused wholly by impulses passing 
down the cranial secretory nerves. But a secretion may, in certain 
circumstances, be caused by impulses passing along the sympathetic 
nerve ; for example, when the central end of a sensory nerve is stimu- 
lated, the secretion, so far as is known, is always accompanied by a con- 
striction of the blood vessels of the gland. 
In man, cases sometimes occur in which there is a permanent absence 
of secretion from the large salivary glands, and from the glands of the 
mucous membrane of the mouth. Such cases are rarer in men than in 
women. In women the loss of secretory power usually comes on after 
middle life, and may be the result of an emotional shock. For some 
time pilocarpine will still cause a secretion of saliva (Hadden), but 
eventually it causes none, though it still causes sweating. 6 The 
absence of secretion is no doubt due to a derangement of the reflex 
nervous mechanism, so that impulses passing up the afferent nerves no 
longer give rise to efferent impulses. The lack of normal functional 
activity probably causes a gradual atrophy of the glands, and a diminu- 
tion of irritability of the nervous and glandular structures, so that 
eventually pilocarpine — or the amount of it which can be given safely — 
no longer produces a flow of saliva. 
1 For an account of papers on the reflex secretion of saliva, cf. Buff, Bcitr. ~. Anat. u. 
Physiol. {Eckhwrd), Giessen, 188S, Bd. xii. S. 3. 
- Ibid., 1876, Bd. vii. S. 44. 
3 Gom.pt. rend. Acad. d. sc, Paris, 1864, tome ix. p. 336. Secretion on stimulation of 
the central end of the vagus was first observed by Bernard, 1S59. 
4 Cf. also Owsjannikow and Tschiriew, Melanges biol. Acad. imp. d. sc. de St.-Piters- 
hour;/, 1872, tome viii. p. 651. 
5 Op. cit. 6 Hutchinson, cf. Hadden, Brain, London, 1889, vol. xi. p. 484. 
