SECRETORY NERVES FOR THE SWEAT GLANDS 399 



pressure is a direct cardiac effect. Stimulate the central end of the vagus 

 which produces a fall of blood pressure through the vaso-motor system. 

 There should be a normal period of at least ten minutes following each experi- 

 ment to allow the secretion of the kidney to return to the normal. 



Expose the splanchnic nerves at the point where they pass beneath the 

 diaphragm into the abdominal cavity. Adjust a pair of shielded electrodes, 

 close the cavity, and, when the animal has returned to the normal uniform 

 rate of secretion and of blood pressure, stimulate the splanchnic nerves. 

 The splanchnics contain vaso-constrictor nerves for the kidney. The onkom- 

 eter experiment should, therefore, demonstrate a sharp decrease in the vol- 

 ume of the organ, while the blood pressure is only slightly changed. The 

 rate of secretion should be followed for at least twenty minutes after stimula- 

 tion of the splanchnics. This test should be repeated two or three times. 



In this connection demonstrate the influence of deep chloroform anesthesia 

 on urinary secretion. The chloroform should be pushed to the danger limit 

 and maintained there for a couple of minutes or more. Compare the rapidity 

 of the recovery of blood pressure with the recovery of the rate of secretion. 



2. Secretory Nerves for the Sweat Glands. Langley has mapped 

 out the paths of the secretory nerves for the sweat glands. He has shown 

 that in the cat these fibers are distributed to the hind limb through the sciatic. 

 Anesthetize a half -grown cat, isolate the sciatic nerve, cut it and stimulate the 

 peripheral end with a medium to strong induction current. After a few 

 moments beads of perspiration will appear on the pads of the foot, which 

 should therefore be carefully examined before the experiment. 



URINE ANALYSIS. 



3. Daily Quantity. Determine the total quantity, for 24 hours, 

 of urine secreted through a period of 3 or 4 days, beginning and ending the 

 period at a definite hour in the day, preferably on rising in the morning. 

 The daily secretion varies through wide extremes, depending upon the quan- 

 tity of liquid taken in the food, the daily exercise, the temperature, etc., etc. 

 In the analysis of urine it is always better to take a mixed 24-hour sample. 



4. Specific Gravity. Determine the specific gravity of 24-hour 

 urine. This is done by the instrument known as the urinometer which 

 carries a graduated scale at the neck. Care should be taken to float the 

 urinometer so that it does not come in contact with the measuring cylinder. 

 The scale should be read at the bottom of the meniscus. 



5. Reaction. Determine the reaction of perfectly fresh urine, using 

 litmus paper. The normal urine is slightly acid under ordinary conditions, 

 due to the presence of acid phosphates or perhaps in some cases to traces of 

 free organic acid. 



After standing some time the reaction is usually alkaline, owing to fer- 



