FOOD AND DIGESTION. 343 



When, on the other hand, the stimulus is applied to the sympathetic 

 filaments (mere division producing no apparent effect), the arteries con- 

 tract, and the blood stream is in consequence much diminished; and 

 from the veins, when opened, there escapes only a sluggish stream of 

 dark blood. The saliva, instead of being abundant and watery, becomes 

 scanty and tenacious. If both chorda tympani and sympathetic branches 

 be divided, the gland, released from nervous control, may secrete con- 

 tinuously and abundantly ( paralytic secretion). 



The abundant secretion of saliva, which follows stimulation of the 

 chorda tympani, is not merely the result of a filtration of fluid from 



\ V6S8e ' i^ (T u ls not intended <*> illustrate the exact anatomical relations of the several struc- 

 QiiWfU 1 * ^ i ?"i A sub-maxillary gland into the duct (sm. d.) of which acamila has been tied, 

 subhngual gland and duct are not shown, n. I, n. I'., the lingual or gustatory nerve ; ch. *., 

 ch. t ..the chorda tympani proceeding from the facial nerve, becoming conjoined with the lingual 

 ^^/.' and Afterward diverging ancf passing to the gland along the duct 'gm. ql, sub-maxillary 

 fwS V SJ? 'p 8 r ? 5' n ' ZM the Iin ^ ual nerve Proceeding to the tongue ; a. car., thecarotid artery, 

 two orancnes of which, a. sm. a. and r. sm. p., pass to the anterior and posterior parts of the gland ; 

 noS'n H antenor and Posterior veins from the gland ending in v.j., the jugular vein ; v. sym., the 

 conjoined vagus and sympathetic trunks ; gl. cer.s., the superior-cervical ganglion, two branches 

 r wmcn forming a plexus, a./., over the facial artery are distributed (n. sym. sm.) along the two 

 glandular arteries to the anterior and posterior portion of the gland. The arrows indicate the 

 ection taken by the nervous impulses ; during reflex stimulations of the gland they ascend to the 

 brain by the lingual and descend by the chorda tympani. (M. Foster.) 



the blood-vessels, in consequence of the largely increased circulation 

 through them. This is proved by the fact that, when the main duct is 

 obstructed, the pressure within may considerably exceed the blood-pres- 

 sure in the arteries, and also that when into the veins of the animal 

 experimented upon some atropin has been previously injected, stimula- 

 tion of the peripheral end of the divided chorda produces all the vascu- 

 lar effects as before, without any secretion of saliva accompanying them. 

 Again, if an animal's head be cut off, and the chorda be rapidly exposed 

 and stimulated with an interrupted current, a secretion of saliva ensues for 

 a short time, although the blood supply is necessarily absent. These 



