746 PHYSIOLOGY 



from this nerve along the chorda tympani to the lingual division 

 of the fifth nerve. The lingual nerve passes below the duct, and 

 just before it crosses the two ducts of the sub-maxillary and retro- 

 or sub- lingual glands it gives off a small branch backwards, namely, 

 the chorda tympani, which runs along the sub-maxillary duct to be 

 distributed to the glands, and in its course gives of fibres also to the 

 retro-lingual (Fig. 321). 



The fibres are apparently finally distributed to the secreting 

 alveoli, where they end freely on the secreting cells just below the 

 basement membrane. They do not, however, take an uninterrupted 

 course. By means of the nicotine method Langley has shown that all 

 the fibres to the sub-lingual and the sub-maxillary glands end some- 

 where near the glands in connection with ganglion-cells. From the 

 ganglion- cells fresh relays of fibres are given off which pass to the 

 gland-cells themselves. The fibres going to the sub-maxillary gland 

 are connected with scattered cells lying in the substance of the gland 

 itself ; those passing to the retro-lingual gland are connected for the 

 most part with ganglion-cells which make up the so-called ' sub- 

 maxillary ganglion.' 



The fibres to the parotid gland pass along the glossopharyngeal 

 nerve and its tympanic branch (nerve of Jacobson) to the tympanic 

 plexus. Hence the fibres are carried by the Vidian nerve to the 

 otic ganglion, and from this ganglion by a communicating branch 

 to the second division of the fifth nerve ; by the auriculo-temporal 

 branches of this nerve the fibres are carried to the gland. 



The sympathetic supply to all these glands is contained in fine 

 filaments on the walls of the arteries with which they are supplied. 

 The fibres are derived ultimately from the spinal cord, whence they 

 issue by the upper three anterior dorsal nerve-roots. They pass 

 into the stellate ganglion, round the ansa Vieussenii to the inferior, 

 and so to the superior cervical ganglion of the sympathetic. Here 

 the fibres end around the cells of the ganglion, and a fresh relay 

 of fibres, chiefly non-medullated, arise from the cells and travel 

 on the walls of the branches of the external carotid artery to their 

 destination. 



The effect of stimulating the peripheral ends of the cerebro- 

 spinal nerves going to the glands presents a general resemblance, 

 whichever be the gland involved. Within a period of half to two 

 seconds after the stimulation has been applied, a secretion of saliva 

 is produced, presenting similar characters to that which would be 

 obtained from the gland under normal conditions if it were provided 

 with a permanent fistula. The concentration of the saliva as well 

 as its rate of secretion depends on the strength of the stimulus. The 

 following Table (Heidenhain) shows the effect on the amount and 



