274 THE HUMAN BODY, 



tion. The evidence is, perhaps, not quite conclusive, but 

 experiments upon the parotid gland of the dog put the 

 matter beyond a doubt. 



The submaxillary gland receives fibres from the sympa- 

 thetic system, as well as the chorda tympani from the 

 cerebro-spinal. Excitation of the sympathetic fibres causes 

 the gland to secrete, but the saliva poured out is differ- 

 ent from that following chorda stimulation, which is 

 in the dog abundant and comparatively poor in organic 

 constituents, and accompanied by vascular dilatation : while 

 the "sympathetic saliva/' as it is called, is less abundant, 

 very rich in mucin, and accompanied with constriction of 

 the gland arteries. According to the above view we 

 might suppose that the chorda contains many transuda- 

 tory and few trophic fibres, and the sympathetic many 

 trophic and few transudatory. It might, however, well be- 

 objected that the greater richness in organic bodies of the 

 sympathetic saliva was really due to the small quantity of 

 blood reaching the gland, when that nerve was stimulated. 

 This might alter the nutritive phenomena of the cells and 

 cause them to form mucin in unusual abundance, in which 

 case the trophic influence of the nerve would be only in- 

 direct. Experiments on the parotid preclude this explan- 

 ation. That gland like the submaxillary gets nerve-fibres- 

 from two sources: a cerebral and a sympathetic. The latter- 

 enter the gland along its artery, while the former, origin- 

 ating from the glosso-pharyngeal, run in a roundabout 

 course to the gland. Stimulation of the cerebral fibres 

 causes an abundant secretion, rich in water and salts, but 

 with hardly any organic constituents. At the same time u 

 produces dilatation of the gland arteries. Stimulation of the 

 sympathetic causes contraction of the parotid gland arteries 

 and no secretion at all. Nevertheless it causes great 

 changes in the gland-cells. If it be first stimulated for a 

 while and then the cerebral gland-nerve, the resulting 

 secretion may be ten times as rich in organic bodies as that 

 obtained without previous stimulation of the sympathetic; 

 and a similar phenomenon is observed if the two nerves be 

 stimulated simultaneously. So that the sympathetic nerve, 



