468 DIGESTION. 



crosses the duct, in order to accompany the hitter to the gland 

 lg. :;i)7). In the an-le which it thus forms with the lin- 

 gual iu-s the lubmaxillary ganglion or gangHonlc plexus above 



mentioned, From it BbrM originate which reach the gland 

 along A Yith the chorda. The sympathetic fibres are derived 

 from the superior cervieal ganglion. 



Physiologically, the nerves derived from the snbmaxillary 

 rriniiiion cannot' be distinguished from those of the chorda. 

 When the chorda is Irritated, the arteries of the inland dilate, 

 the bloodstream In-coming much more rapid; consequently, 

 the veins leading from 1 he organ pulsate, and if they are opened 

 thevjet like an artery. At t he same time, the secretion dis- 

 cha'rued from the duct becomes copious and watery. When 

 tin' sympathetic tibvcv :U e excited, the arteries contract . and 

 tlu- Circulation in the gland is retarded, and if the veins are 

 opened, they discharge" black" blood in a slow stream. The 

 tion becomes scanty ami tenacious. 



:t s tirst demonstrated experimentally by Ludwig that the 

 tion produced by excitation of the chorda is 

 immediately dependent on increased activity of the function of 

 civting elements of the gland, and not on changes in the 

 in other \vords. that in the submaxillary gland 

 the process of secretion ^ nnh n ynprjf_filt r.-it ion. Ult is effected 

 bv changes, which goon within the gland itself, of such a nature 

 rmine a current from the circulating blood towards 

 the duct. This conclusion was based by Ludwig on the ob- 

 ion : first, that if the duct is constricted, secretion con- 

 tinues, notwithstanding that the pressure in the interior of the 

 gland is greater than that in the arteries; and, secondly, that 

 ion continues after circulation has ceased, r. j/., after the 

 head has been severed from the body. 



6 recent observations make it probable that by thecAorcfa 

 tymjiatii two kinds of fibres find their way to the gland, viz., 

 fibres by which secretion is intluenced directly, and others 

 which arc " vaso-inhibitory." /. >.. diminish arterial tonus. 

 Among the most important observations bearing on this ques- 

 tion art* those lately published by J leidenhain. who has found 

 that injection of atropia into the arteries or veins of an animal 

 deprives the chorda of its power of over-secretion, without in- 

 ing with its vaso-inhibitory function ; and the earlier ex- 

 ents of (liann/./.i. made under Ludwig's directions, in 

 which a similar effect was produced by the injection of solution 

 of quinine, half per cent, hydrochloric acid, or five per cent, 

 solution of .sodium carbonate into the gland itself. 



** 92. Demonstration of the Functions of the Chorda 

 Tympani and Sympathetic Fibres of the Submaxil- 

 lary Gland in the Dog. The animal having been secured, 

 as directed in SS. and placed under chloroform, with the 



