l.'ii TIIK XKKYOIS SYSTP:M AND ITS COXSKRVATION 



nomic >ystem includes nerve-paths of the standard type 

 (preganglionic and postganglionic fibers) to many organs 

 of secretion. 'I'Jiis is conspicuously Ilic case with the 

 sweat-glands. It is true, too, of the tear-glands, the sali- 

 vary glands, and those in the lining of the stomach. It is 

 certainly true of the adrenal bodies and probably of the 

 pancreas. There is less certainty regarding a direct 

 nervou- control of the intestinal glands, the liver, and the 

 kidneys. \Yhen glands are active it is to be expected that 

 va.Mimotor support will be given to them through the wide- 

 dilation of their blood-vessels. But the kind of nervous 

 control of which we are now speaking is believed to be 

 exerted upon the epithelial cells forming and discharging 

 the product. Typic secretory activity may be promoted 

 in two ways by the autonomic system: by this direct 

 stimulation of the working cells .of the gland and, indi- 

 rectly, by the enlisting of the vasomotors to secure a freer 

 circulation. In some glands for example, the kidney- 

 it is the volume of the blood-flow on which the performance 

 of the gland chiefly depends. When this is the case it be- 

 comes difficult to decide whether government of the other 

 order, that is, by true secretory fibers, surely exists. 



