394 DIGESTION 



the interior of Wharton's duct. But such measurements are open 

 to many fallacies; and while there is no doubt that more heat is 

 produced in the active than in the passive gland, it will not be 

 surprising, when the vastly-increased blood-flow is remembered, 

 that no difference of temperature between the incoming and out- 

 going blood has been satisfactorily demonstrated. 



It has already been mentioned that most of the fibres of the chorda 

 tympani proper become connected with ganglion-cells, and lose their 

 medulla inside the submaxillary gland, only a few having already lost 

 it by a similar connection with ganglion-cells in the chordo-lingual 

 triangle. These facts have been made out by means of the nicotine 

 method previously described (p. 182). 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 sympa- 

 thetic plexus on the submaxillary artery, but to stimulation 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 con- 

 nected with fibres going to the sublingual. In a similar way, by observ- 

 ing 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 ' (p. 376). 



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 iatter, 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 



