74 LABORATORY MANUAL OF GENERAL PHYSIOLOGY 



of the tissue, then remove the whole digestive tract by severing the 

 esophagus and rectum. 



Place frog on zinc pan, with plasticine supports arranged as in 

 demonstration. 



Holding spleen in forceps, trace splenic artery back to junction with 

 abdominal aorta. Pass ligature under aorta. Delicately cut half way 

 through aorta and insert cannula N from reservoir with colorless medium. 

 Tie ligation. Insert other cannula M into vena abdominalis, likewise 

 tying tip in place. CANNULAE SHOULD BE INSERTED WITH 

 LIQUID FLOWING, to avoid air bubbles. 



Cut away urinary bladder and find seminal vesicles and ureters. Under 

 binocular microscope, incise vesicles and insert cannulae into the ureters. 

 Tie in place. Watch preparation to see that flow of liquids is not blocked. 

 In one-half hour note liquid issuing from ureters. Instead of cannulating 

 ureters you may catheterize cloaca after an hour as in Ex. 15 (a). Text 

 p. 246. 



(c) Simple Experiment on the Permeability of the Kidney. — For the 

 benefit of students who find experiments (a) and (b) too tedious the 

 following simple experiment is included. 



In an anesthetized frog make an incision in the ventral surface of the 

 body wall from the pelvic region upwards through the pectoral girdle, 

 cutting as few blood vessels as possible. If bleeding occurs cauterize the 

 spot with a heated wire. Divide the skin and muscles of the abdominal 

 wall on the right side by a transverse incision at the level of the kidney 

 extending around the vertebral column. Divide the peritoneum on a 

 line running parallel to the lateral border of the right kidney. Place 

 the frog on a board or piece of heavy card board provided with a hole for 

 microscopical observation. Pin the animal down to prevent reflex 

 movements. Pin the kidney over the opening in the board. Avoid 

 injury to the vascular system of the kidney. The region between the 

 adrenal gland and the edge of the kidney is to be observed. The ventral 

 surface of the kidney must be horizontal. Place a cover glass over the 

 kidney to prevent evaporation. Keep the animal moist with cloth 

 soaked in Ringer. Put the frog board on the stage of a microscope with 

 light reflected through the kidney. Use low power. Locate the 

 glomeruli. Prepare a hypodermic syringe with 0.5% indigo carmine. 

 One student slowly injects half a cc. of dye into the heart while his partner 

 watches through the microscope. If all goes. well, the dye will appear 

 in the arteries and glomeruli in a few seconds. Observe the blue particles 

 in the walls of the renal tubules. If time permits observe the effects of 

 injected glucose and of adrenalin. 



A complete bibliography on the secretion of dye stuffs by the kidney 

 will be found in the recent paper by Hober, Jour. Cell. Comp. Physiol., 6: 

 117, 1935. The comparative physiology of the kidney is reviewed by 



