384 DISSECTION OF THE RABBIT. 



X. DISSECTION OF THE BRAIN. 



The brain should be removed directly after the rabbit is 

 killed,' and placed at once in strong spirit or the mixture given 

 below, as it decomposes rapidly. It is well to put a loose pad 

 of cotton wool in the bottom of the bottle, and place the brain 

 upon it, in order to prevent flattening from contact with the 

 glass, and to ensure free access of the spirit to all parts of the 

 surface ; the brain should be turned over after it has been a 

 few hours in spirit. 



To remove the brain, first shin the head ; then expose the 

 brain by snipping away, with the bone forceps, the roof and 

 sides of the skull, beginning at the foramen magnum, and 

 working forwards. Take special care in the region of the ears 

 to avoid injury to the fioccular lobes of the cerebellum, which 

 are lodged in the fioccular fossae of the periotic bones (p. 311). 



Having completely removed the roof and sides of the cranium 

 and cut through the dura mater, a tough fibrous membrane 

 which lines the cranial cavity, cut across the spinal cord about 

 half an inch behind the foramen magnum, and turn out the 

 brain from behind forwards, lifting it up gently with the handle 

 of a scqlpel. 



Note and identify the several nerve-roots as you do so, and 

 cut through them in order, close to the skull-wall, so as to leave 

 as much of the roots as possible attached to the brain. 



Place the brain in spirit or a mixture of equal parts of one 

 per cent, potass, bichromate and eight per cent, formalin at 

 once, handling it with great care, as it is very soft and easily 

 damaged. Leave it in spirit for three or four days, or in the 

 mixture three weeks ; after which wash in water for a day, and 

 then dissect it as described below. 



The several divisions of the rabbit's brain are the same 

 as those of the brain of the dog-fish, the most important 

 differences between the two being (1) the great size of the 

 cerebral hemispheres, which overlap and conceal the dorsal 

 and lateral surfaces of the thalamencephalon and optic lobes ; 

 (2) the greater size and more complicated structure of the 

 cerebellum ; (3) the much greater development of the trans- 



