INFLUENCE OF NERVES ON SECRETION. 271 



it is clear that the activities of both, though correlated, are 

 essentially independent. The contraction is not due to the 

 greater blood-flow for, not only can an excised muscle en- 

 tirely deprived of blood, be made to contract by stimulating 

 its nerves, but in an animal to which a small dose of curari 

 the arrow poison of certain South American Indians has 

 been given, stimulation of the nerve will cause the vascu- 

 lar dilatation but no muscular contraction: the curari par- 

 alyzing the motor fibres, but, unless in large doses, leaving 

 the vaso-dilators intact. The muscular fibres themselves 

 are unacted upon by the poison, as is proved by their 

 ready contraction when directly stimulated by an electric 

 shock. 



Now let us return to the salivary glands and see how far 

 the facts are comparable. The main nerve of the submax- 

 illary gland is known as the chorda tympani. If it be di- 

 vided in a narcotized dog, and a tube placed in the gland- 

 duct, no saliva will be found to flow. But on stimulating 

 the peripheral end of the nerve (that end still connected 

 with the gland) an abundant secretion takes place. At 

 the same time^ there is a great dilatation of the arteries of 

 the organ, much more blood than before flowing through 

 it in a given time: the chorda obviously then contains vaso- 

 dilator fibres. Now in this case it might very well be that 

 the process was different from that in a muscle. It is con- 

 ceivable that the secretion may be but a filtration due to 

 increased pressure in the gland capillaries, consequent 

 on dilatation of the arteries supplying them. If a greater 

 filtration into the lymph spaces of the gland took place, this 

 liquid might then merely ooze on through the secreting cells 

 into the commencing ducts and, as it passed through, dis- 

 solve out and carry on from the cells the specific organic 

 elements of the secretion. Of these, in the submaxillary 

 of the dog at least, mucin is the most important and 

 abundant. That, however, the process is quite different, 

 and that there are in the gland true secretory fibres in ad- 

 dition to the vaso-dilator, just as in the muscle there are 

 true motor fibres, is proved by other experiments. 



If the flow of liquid from the excited gland were merely 



