CRANIAL AND SPINAL CAVITIES 401 



Cranial and Spinal Cavities. 



29. In some instances it may be necessary (e. g., 

 experimental inoculation of rabies) to examine the 

 cranial cavity or to remove the spinal cord. Return 

 the viscera to the adbominal cavity; draw the flaps of 

 skin together and secure with Michel's steel clips. 

 Draw the copper nails securing the limbs to the board, 

 reverse the animal and again nail the limbs down the 

 body now being dorsum uppermost. 



30. Make a longitudinal incision in the mesial line 

 from snout to root of tail, and four transverse incisions 

 one joining the roots of the two ears, one across the 

 body at the level of the spinis of the scapulae, another 

 at the level of the costal margin and the last across the 

 upper level of the pelvis. Reflect these flaps of skin. 



3 1 . With forceps and scalpel dissect out the muscles 

 lying in the furrow on either side of the spinal processes. 



32. Cut through the bases of the transverse processes 

 with bone forceps. Cut away the vault of the skull, 

 cut through the roots of the nerves and remove the brain 

 and spinal cord, place in a large glass dish for examina- 

 tion. Prepare cultivations from the cerebro-spinal 

 fluid. The removal of the brain and cord is a tedious 

 process and during the dissection it is difficult to avoid 

 injury to these structures. 



The operation is, however, carried out very 

 expeditiously and neatly with the aid of the surgical 

 engine (vide page 361). A small circular saw is fitted 

 to the hand piece. The bones of the skull are cut 

 through and the whole of the vault removed, exposing 

 the entire vertex of the brain. Similarly all the spinous 

 processes can be removed in one string by running the 

 saw down first one side of the spinal column and then 

 the other. In this way ample space for the removal 

 of the nervous tissues is obtained with a minimum 

 of labour. 

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