210 ADVANCED LESSONS IN PRACTICAL PHYSIOLOGY 



2. Function of the Chorda Tympani Nerve. Stimulate the chorda 

 tympani for fifteen seconds and count the number of drops of saliva which 

 escape during this time. Observe the degree of viscosity of the saliva. 

 Pour it from one beaker into another, noting its viscidity. Repeat this 

 test. 



3. Function of the Sympathetic Nerve. Stimulate the central end 

 of the sympathetic nerve and count the number of drops of saliva. Ob- 

 serve its viscosity and viscidity. Contrast it with the chorda saliva. 



4. Secretory Pressure. Record on the kymograph the blood- 

 pressure prevailing in the carotid artery of this animal. Disconnect 

 the carotid artery from the manometer and connect the latter with the 

 duct of the submaxillary gland. Stimulate the chorda tympani for a 

 considerable time, with occasional intervals of rest, and record the 

 pressure under which secretion still takes place. Allow the drum to 

 revolve very slowly. The pressure in the salivary duct may be raised 

 a considerable distance above the general blood-pressure, proving thereby 

 that filtration is not the only factor concerned in the formation of this 

 secretion. Enumerate the other factors. 



5. The Vasomotor Changes in the Submaxillary Gland Produced by 

 Stimulation of the Chorda Tympani and Sympathetic Nerve. Reflect 

 the skin and expose the large veins in the vicinity of the submaxillary 

 gland. Ligate the internal maxillary and facial veins opposite the 

 anterior end of the gland, and ligate the sublingual vein about 2 cm. 

 distally to its junction with the facial vein. Carefully destroy by tor- 

 sion the larger cutaneous veins which empty their contents into the 

 aforesaid veins centrally to the ligatures. The vein which returns the 

 blood from the submaxillary gland pursues a very irregular course. In 

 most cases, however, it joins one or the other cf the above-mentioned 

 veins at a point nearer to the heart than where the ligatures have been 

 applied. If this relationship prevails in the mammal used for this 

 experiment, only the blood returned from the submaxillary gland will 

 be able to enter the external jugular vein. 



Insert a cannula in the distal end of the external jugular vein near 

 the point where the internal and external maxillary veins unite. Con- 

 nect the cannula with a bottle having an inlet and an outlet tube, and 

 containing a solution of magnesium sulphate. When the blood is al- 

 lowed to flow into the bottle it will displace an equal quantity of this 

 solution, which can be measured in a graduated cylinder. 



Measure the blood flow for a short time, then stimulate the chorda 

 tympani nerve until you have obtained a decided increase in the blood 

 flow. Allow this flow to become normal again. Stimulate the sympa- 

 thetic nerve until the blood flow has been considerably lessened. These 

 results are referable to the fact that the chorda possesses vasodilator 

 qualities, whereas the sympathetic is a vasoconstrictor nerve. 



6. Secretion by the Bloodless Gland. Render the submaxillary 

 gland bloodless by ligating the blood-vessels supplying the head, or by 

 decapitating the animal. Stimulate the chorda tympani, and measure 



