SECRETION DIGESTION ABSORPTION. 



to the duct, runs backward to the gland. This is the chorda tym- 

 pani (Fig. 36, T). 



Pass a thread under the chorda to use later in handling the 

 nerve for stimulation. Divide the hypoglossal nerve and expose 

 the sympathetic filaments. Pass a thread around these also. Iden- 

 tify the submaxillary duct and introduce and tie a cannula into it. 

 The cannula should end in a small rubber tube. This is closed 

 by an artery clip until it is desired to collect the secretion. The 

 introduction of the cannula may be facilitated by first stimulat- 

 ing the chorda for a short time with a weak tetanizing current, 

 thus distending the duct with secretion. 



Small graduated glass cylinders are provided for collecting the 

 secretion from the cannula in the gland duct. These may be 

 changed at any desired interval of time, say every five or ten 

 minutes. The rate of flow is determined by the amount of 

 secretion eliminated in a given time period. 



1. Observe the rate of flow from the gland before stimulation. 

 Has the anaesthetic any stimulating influence on the salivary flow ? 

 This observation should cover a period of five minutes. 



2. Stimulate the chorda with a weak tetanizing current. How 

 is the rate of salivary flow affected ? Compare the appearance of 

 the blood-vessels of the gland during stimulation of the nerve with 

 the vascular condition before stimulation. 



3. Allow the preparation to rest for several minutes. Stimulate 

 the sympathetic. Is there any marked effect on the rate of flow ? 

 What is the effect upon the condition of the blood supply to the 

 gland ? 



4. Paint the submaxillary ganglion with a o.i-per-cent solution 

 of nicotine. Nicotine, in weak solution, paralyzes nerve cells, but 

 not nerve fibres. Stimulate the chorda again. Is there still an ac- 

 celerator effect on the salivary secretion? Are the fibres of the 

 chorda broken by nerve cells in this ganglion ? 



Now paint the chorda with nicotine where it enters the hilum of 

 the gland. Stimulate the chorda again. Is there any effect on the 

 flow of the secretion ? Stimulate at the hilum itself. Is there any 



