DIGESTION 365 



method previously described (p. 165). Thus, it is found that, after 

 the injection of nicotine (5 to 10 mg. in a rabbit or cat, 40 or 50 mg. 

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

 lingual nerve causes no secretion from the submaxillary gland ; but 

 stimulation 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 sympathetic plexus on the submaxillary artery, but to stimula- 

 tion of chorda fibres beyond the hilus, is shown by the fact that 

 after atropine has been injected in sufficient amount to paralyze the 

 nerve endings of the chorda, but not of the sympathetic, stimulation 

 of the hilus causes little or no flow of saliva. The application of 

 nicotine solution to the chordo-lingual triangle does not affect the 

 submaxillary secretion 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 

 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 mode- 

 rately 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 exam- 

 ination 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 ' (p. 347). 



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, thick 

 and rich in organic matter. With strong stimulation of both 

 nerves, the secretion, at first plentiful and watery, soon dimin- 

 ishes, even below the amount obtained by stimulation of the 

 chorda alone, because of the diminution in the blood-flow, and 

 therefore in the oxygen supply, produced by the vaso-constrictbrs 



