484 THE SALIVAR Y GLANDS. 



The sympathetic nerve-fibres are connected with nerve-cells in the 

 superior cervical ganglion. If the cervical sympathetic be cut, the end 

 towards the ganglion gives, in about four days, no effect on stimulation, 

 but stimulation of the ganglion itself or of the fibres beyond it causes 

 secretion and pallor of the gland (p. 522). On microscopical examination, 

 the nerve-fibres are found to be degenerated, as far as the ganglion 

 but not beyond it. Injection of nicotine causes for a time, varying with 

 the dose, effects like those caused by degeneration of the nerve. 1 In 

 the cat even 5 mgrms. of nicotine may be sufficient to paralyse the cervical 

 sympathetic for a time, but very large amounts, e.g. 500 mgrms., do not 

 paralyse the nerves beyond the ganglion. From this and from other 

 facts we deduce that the sympathetic fibres are not connected with any 

 sympathetic nerve- cells peripherally gf the superior cervical ganglion ; 

 and there are reasons for believing that they are not connected with 

 any nerve-cells between the ganglion and the spinal cord. In the dog 

 the cervical sympathetic is much less readily paralysed by nicotine. 



Secretion of saliva produced by stimulation of the medulla 

 oblongata. Bernard 2 found that puncture of the fourth ventricle in 

 the dog causes secretion from all the salivary glands, and if the puncture 

 be a little above the spot, injury of which produces diabetes, the secre- 

 tion may be confined to the submaxillary gland, and from this gland may 

 be abundant. Loeb 3 showed that puncture of the medulla caused a greater 

 secretion from the submaxillary or the parotid gland, according as the 

 puncture was in the region of the nucleus of the ninth or of the seventh 

 nerve respectively. With puncture on one side, the effect on the sub- 

 maxillary gland of the opposite side was much greater than on the 

 parotid of the opposite side. Griitzner and Chtapowski 4 observed that 

 stimulation of the medulla oblongata caused abundant secretion if the 

 chorda tympani was intact, a slight secretion if it was cut, but none 

 after section of both the chorda and the sympathetic. 



Secretion of saliva produced by stimulation of the cerebral cortex. 

 It is not clear that the cortex of the cerebral hemispheres is connected 

 with secretion or indeed with any visceral phenomenon in the way 

 in which it is connected with the various body movements. 



Stimulation of the motor area, taking the matter broadly, causes 

 secretion from the salivary glands, more readily than does stimulation of 

 any other part of the cortex. So far as the experiments go, the region 

 which causes maximum secretion from the submaxillary gland causes 

 also maximum secretion from the parotid. Apparently the secretion 

 ceases on cutting the cranial secretory nerve. 



The experiments in which the portions of the cortex which cause 

 secretion have been mapped out were made on dogs under curari. 

 Those who have experimented on undrugged animals find that stimula- 

 tion of the facial area causes no secretion so long as the resulting move- 

 ment is confined to the facial muscles, and Eckhard 5 states that the 

 secretion of saliva from the submaxillary glands only begins when the 

 stimulus is continued long enough, or is made strong enough, to induce 



1 Langley and Dickinson, Proc. Roy. Soc. London, 1889, vol. xlvi. p. 425 ; Langley, 

 Journ. PhysioL, Cambridge and London, 1890, vol. xi. p. 131. 



2 " Le9ons de physiol. expe"rimentale," 1856, Bd. ii. 



3 Op. cit., supra. 



4 Arch. f. d. ges. PhysioL, Bonn, 1873, Bd. vii. S. 522. 



5 Neurol. Centralbl., Leipzig, 1889, p. 65. Of. also Beitr. z. Anat. u. Physiol. 

 (Eckhard), Giessen, 1876, Bd. vii S. 199. 



