336 A MANUAL OF PHYSIOLOGY 



dog), stimulation of the chorda tympani proper or of the chordo-lingual 

 nerve causes no secretion from the submaxillary gland; but stimula- 

 tion of the hilus of the gland is followed by a copious secretion as 

 much, if the stimulation is fairly strong, as was caused by excitation 

 of the nerve before injection of nicotine. That this is due neither to 

 any direct action on the gland-cells, nor to stimulation of the sym- 

 pathetic plexus on the submaxillary artery, but to stimulation of 

 chorda fibres beyond the hilus, is shown by the fact that after atropia 

 has been injected in sufficient amount to paralyze the nerve endings 

 of the chorda, but not of the sympathetic, stimulation cf the hilus 

 causes little or no flow of saliva. The application of nicotine solution 

 to the chordo-lingual triangle does not affect the submaxillary secre- 

 tion caused by stimulation of the chordo-lingual nerve, even in cases 

 where a few secretory fibres for the submaxillary do not leave the 

 chordo-lingual nerve in the chorda tympani proper, but are given off 

 to the chordo-lingual triangle. This shows that none of the ganglion- 

 cells in the triangle are connected with the cerebral secretory fibres 

 of the submaxillary gland. By observations of the same kind they 

 are known to be connected with fibres going to the sublingual. In 

 a similar way, by observing the effects of stimulation of the chorda 

 on the bloodvessels before and after the application of nicotine, it 

 has been found that the vaso-dilator fibres are connected with 

 ganglion-cells in the same positions as the secretory fibres (Langley). 



Stimulation of the Sympathetic Fibres, The sympathetic, as 

 has been already indicated, contains both vaso-constrictor 

 and secretory fibres for the salivary glands. If the cervical 

 sympathetic in the dog is divided, and the cephalic end 

 moderately stimulated, a few drops of a thick viscid and 

 scanty saliva flow from the submaxillary and sublingual 

 ducts, while the current of blood through the glands is 

 diminished. As a rule, no visible secretion escapes from the 

 parotid, but microscopic examination shows that many of 

 the ductules are filled with fluid, which is apparently so 

 thick as to plug them up (Langley) ; while the cells show 

 signs of ' activity.' 



Simultaneous Stimulation of Cranial and Sympathetic Fibres. 

 When the chorda and sympathetic are stimulated together* 

 the former prevails so far, with moderate stimulation of the 

 latter, that the submaxillary saliva is secreted in considerable 

 quantity, and is not particularly viscid ; it is, however, richer 

 in organic matter than is the chorda saliva itself. When 

 the chorda is weakly, and the sympathetic strongly excited, 

 the scanty secretion (if there is any) is of sympathetic type, 



