LESSON XLVIII 



EXCRETION 



SECRETION OF URINE 



1. The Drop Method of Registering the Flow of Urine. Anesthetize 

 a mammal and continue the anesthesia throughout the following experi- 

 ments: Perform tracheotomy. Expose the left common carotid artery 

 and insert in it a straight glass cannula. Fill it with a solution of sodium 

 carbonate, and connect it with the mercury manometer. Isolate the 

 vagus nerve on the same side and place it in a loose silk ligature. On 

 the opposite side expose the external jugular vein. Clamp it centrally; 

 ligate it about 2 cm. distally to the clamp, and insert a straight glass 

 cannula toward the heart. Fill this cannula with normal saline solution. 



Open the abdominal cavity in the linea alba below the umbilicus. 

 Identify the bladder and the two ureters leading away from its posterior 

 surface. Insert a straight cannula in each (toward the kidney) and 

 connect them by means of short pieces of rubber tubing with a Y-tube. 

 Allow the end of the Y-tube to project beyond the edge of the board, at 

 a distance of about 20 cm. above the spoon-shaped lever of the receiving 

 tambour. Connect the latter by means of a long piece of rubber tub- 

 ing with a recording tambour placed against the paper of the kymograph. 

 Adjust the recording needle of the mercury manometer in such a way 

 that it registers in the same ordinate as the writing lever of the record- 

 ing tambour. Allow a chronograph to register seconds below these 

 levers. 



2. Normal Secretion of Urine. Allow the kymograph to revolve at 

 a moderate speed, and register the drops of urine secreted in relation 

 with the curve of the blood-pressure. Remember that the formation of 

 urine is often greatly lessened during ether narcosis. If this condition 

 prevails in the animal used for this experiment, stimulate the flow in 

 the manner described in paragraph 3. 



3. Action of Glucose. Prepare a concentrated solution of glucose 

 (25 c.c.). Filter it and draw 10 c.c. of the filtrate into a pipet. Con- 

 nect the latter with the cannula inserted in the external jugular vein. 

 Allow this quantity of glucose to enter the circulation, but slowly, so 

 that the height of the blood-pressure is not altered. After a certain 

 latent period drops of urine will be seen to enter the Y-tube at intervals. 

 Observe the rapidity with which they are secreted. It is said that 

 glucose stimulates the renal cells directly, giving rise to diuresis. 

 Record the flow in relation with the blood-pressure. 



4. Action of Sodium Chlorid. When the diuresis produced by the 

 glucose has nearly subsided, inject 100 c.c. of warmed saline solution. 

 Register the flow of urine in the manner described above. Repeat the 

 injection if the effect is not sufficiently decisive. 



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