426 EXCRETION 



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 anesthe- 

 sia 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 urinom- 

 eter 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, o\ving to fer- 

 mentation processes. The reaction may vary also according to the food, 

 vegetable foods tending to produce alkaline urine, while with animal foods 

 the reaction is acid. 



6. The Total Quantity of Solids. Determine the solids of urine 

 by evaporating 25 c.c. of a mixed sample of urine to dryness in a weighed 

 platinum or porcelain dish over a water bath. The residue should be dried 

 to constant weight in a drying oven at 105 C. 



A useful rule for approximately estimating the total solids in any given 

 specimen of healthy urine is to multiply the last two figures representing the 

 specific gravity by 2 . 33. Thus, in urine of specific gravity 1025, 2.33X25 = 



