420 ON SOME FUNCTIONS OF THE ENCEPHALON. 



third of an inch in diameter, and then slipping the blade of the 

 scissors from one hole to the other between the bone and the 

 dura mater, and cutting the bone through. The rest of the 

 roof may then be removed piecemeal. Carefully avoid wound- 

 ing the venous sinuses, and carry the operation through as 

 speedily as possible. The amount of ether or chloroform given 

 should be no more than is absolutely necessary just to send 

 the animal off. Previous ligature of the carotid does very 

 little good, and only complicates the operation. 



The animal will not survive the operation very long, but for 

 several hours after the operation the phenomena of complicated 

 movements consequent on stimulation, with total absence of 

 volition, may be witnessed as in the bird and in the frog. 



06s. VIII. Division of (he Semi-circular Canals. This is 

 best performed on the bird, ex. gr., a young pigeon. The stu- 

 dent should first make himself acquainted with the position and 

 relation of the canals in a dead bird. Make a vertical incision 

 along the back of the head, hook back the flaps of skin, scrape 

 away the insertion of the muscles of the neck, remove the outer 

 tablet of the diploe of the skull behind each ear, and pick away 

 in minute pieces with a small pair of forceps the cancellous 

 bone, embedded in which the hard bony canals will then easily 

 be found. 



I hiving thus determined their exact position in the dead bird, 

 the student will find no groat difficulty in reaching them by a 

 similar proceeding in the living body. Having found them, cut 

 one or, better still, two on each side right through with a pair 

 of small but strong scissors. The bleeding, which is generally 

 >sive, may be staunched by styptics. 



Immediately after the operation, and for an indefinite time 

 afterwards, the bird exhibits the utmost disorder in its move- 

 ments. Though able apparently to move each and every mus- 

 cle of its body, it lias completely lost the so-called co-ordina- 

 ting power. For a particular account of this condition, see 

 Flourens's Systeme Nerveux, p. 454, and Goltz Pfliiger's Archiv. 

 Vol. III. p. 172. 



