PRACTICAL EXERCISES 191 



the deep layer of the skin without coming through to the surface 

 may be employed. The wound is to be protected by a coating of 

 collodion. No other dressing is required. The animal is now re- 

 moved from the holder and put back to its hutch. The student must 

 examine it at least once a day for the next week, and study the 

 differences between the two ears (p. 151) and the two pupils. 



25.* Stimulation of the Depressor Nerve in the Rabbit. Set up 

 the apparatus for a blood-pressure tracing as described in 19 (p. 185). 



FIG. 75. ARTIFICIAL SCHEME TO ILLUSTRATE A METHOD OF MEASURING 

 THE CIRCULATION-TIME. 



B, bottle containing water, the rate of outflow of which is regulated by screw clamp 

 a; S, syringe filled with methylene-blue solution, connected with T-piece A ; M, beaker 

 containing methylene-blue solution ; b, c t screw-clamps ; C, T-piece, inserted in the 

 course of the flexible tube E, and connected with the glass tube T, which is filled with 

 beads ; F, outflow tube. The clamp c having been closed and b opened, the syringe is 

 filled with the methylene-blue solution, b is then closed, c opened, and a definite 

 quantity of the solution injected into the system. The time from the beginning of 

 injection till the appearance of the blue at G is measured with the stop-watch. 



Arrange an induction coil and electrodes for an interrupted current. 

 Anaesthetize a rabbit with J gramme chloral hydrate, and if necessary 

 with ether. For blood-pressure experiments only small doses of 

 chloral hydrate or chloroform can be given, as they affect the vaso- 

 motor centre. Put the animal on the holder. Insert a cannula in 

 * This experiment is only suitable for advanced students. 



