Sympathetic Innervation 51 



most glands, however, sympathetic stimulation has some further 

 effect on the gland apart from the vascular effect (discussed in 

 Chapter VII). Such an effect, apparently exerted on the secretory 

 cells, has been demonstrated in different ways. 



1. In some glands, such as the parotid gland of the dog, micro- 

 scopical changes have been seen in the gland cells. 



2. It can further be seen as an "augmented secretion" in Lang- 

 ley's sense, in which sympathetic stimulation has a real secretory 

 effect, increased because the excitability of the gland cells has been 



20 



IS 



10 



5 - 



J 



ii. nliili.l.. 



i. 



Fig. 3.4. Augmented secretion in a cat in dial anaesthesia. 



Atropine had been given in a dose which abolished the secretory effect of chorda stimulation. 

 The sympathetic nerve was stimulated for periods of i minute at 6-minute intervals. The vertical 

 columns represent the submaxillary secretion in divisions of the graduated tube (i division 

 = 4-5 /A.). The points marked c on the lower line indicate that the chorda, which alone produced 

 no secretion, was stimulated for the 60 seconds just preceding the sympathetic stimulation 

 (Macintosh and Rawlinson, 1035)- 



raised, for instance by a previous stimulation of the parasym- 

 pathetic fibres. The existence of such a "true augmented secretion" 

 (Babkin) was well demonstrated in the following way (Macintosh 

 and Rawlinson, 1935), illustrated in Fig. 3.4. A small dose of 

 atropine had been given, just big enough to abolish the secretory 

 effect of the chorda tympani on the submaxillary gland of the cat. 

 Stimulation of the chorda was nevertheless found to increase the 

 secretory effect of subsequent stimulation of the sympathetic fibres. 

 The effect of the chorda stimulation could obviously not be to fill 

 the ducts with saliva for a contractile mechanism activated by sym- 

 pathetic stimulation to exert an expulsive action on; the augmented 

 effect was not due to vasodilatation in the gland caused by the 



