LABORATORY MANUAL OF PHYSIOLOGY. 



VIII. DIVISION OF THE SEMICIRCULAR CANALS. 



A young pigeon serves best for this purpose. It is well to make 

 a dissection on a dead bird first in order to become familiar with 

 the position and relations of the canals. Make a transverse in- 

 cision through the skin of the head. Slip these flaps back so as to 

 expose the bone. Scrape away the insertions of the neck muscles. 



3 



s. 



I 



\ 



FIG. 2i. Semicircular Canals (Pigeon). Outer plate of skull and cancellous bone 

 removed to expose the semicircular canals : i, Superior (vertical); 2, posterior (verti- 

 cal) ; and 3, anterior (horizontal) . The planes of i, 2, and 3 cut each other at right 

 angles. 



Remove the outer table of the skull behind each ear, carefully re- 

 moving with the forceps the cancellous or spongy bone between the 

 two plates until the canals are seen (see Fig. 21). 



Having made the preliminary dissection on a dead bird, repeat 

 the same process on a live pigeon under the influence of chloro- 

 form. After the canals are exposed, cut through one or two of 

 them, with strong scissors, making a careful record of the canals 

 thus injured. Control the bleeding with suprarenal extract. 



If the bird recovers from the immediate effects of the operation, 

 carefully observe and note its departure from the normal condi- 

 tion of the pigeon with the semicircular canals intact. Compare 

 the behavior of this pigeon with that of the pigeon which had its 

 cerebellum removed. 



[54] 



