HISTOLOGICAL DEMONSTRATIONS. 139 



The posterior pyramids are now difficult to distinguish from 

 these. They contain gray matter. The floor of the fourth 

 ventricle with its gray matter is evident. 



CEREBELLUM AND CEREBRUM. 



247. Methods. a. The methods of preparation are 

 similar to those recommended for the spinal cord and me- 

 dulla. The brain, however, cannot bear a solution of 

 chromic acid so strong as that recommended for the cord. 

 The dilute solution of chromic acid and potass, bichrom. 

 (Solution 4, 4), used as directed in 14, gives good results. 

 The sections are treated as in the case of the spinal cord. 



b. The brain may also be hardened first in rectified 

 spirit, and then in a 2 per cent solution of potass, bichrom. 



c. The cells of the cerebrum may be prepared for examination in 

 their fresh condition by a method devised by Mr. Lewis of Wakefield 

 (Monthly Microscop. Journal, vol. xvi. p. 105). The pia mater is 

 stripped from a convolution of the human cerebrum as fresh as possible. 

 Thin vertical sections of the gray matter are then made with a broad- 

 bladed and perfectly sharp razor, the surface of which is deluged with 

 spirit. As thin a section as possible is floated from the razor upon a 

 slide, and Miiller's fluid is added, to make a pool of fluid above and 

 below the section, so that the tendency of the nervous matter to adhere 

 to the glass during the next process may be diminished. The cover-glass 

 is then applied and cautiously pressed down with the point of a needle 

 applied to its centre, until the nervous matter becomes a thin trans- 

 parent film. The slide is then placed in a flat dish and covered with 

 methylated spirit. After about forty seconds the slide is removed from 

 the dish, one edge of the cover-glass is steadied with the finger, while 

 the other is slowly raised with the point of a scalpel. The spirit faci- 

 litates the removal of the cover-glass, and the nerve film is left floating 

 on the slide, or adhering to the cover-glass. To stain the nerve cells 

 a drop of a i per cent solution of aniline black ( 325) is placed on the 

 film. When the colour is sufficiently deep the slide is lowered under 

 water in a shallow vessel, and washed by gently moving the water with 

 a brush. Previous to mounting, the slide, with the film uncovered, is 

 placed under a bell glass with sulphuric acid, and when perfectly dry 

 a few drops of clove oil, or still better, chloroform, are placed on the 

 film, then a drop of dammar, and then the cover-glass. Staining agents 

 other than the above mentioned may be used. 



248. Structure of Cerebellum. V. S. cerebellum of 

 man or of cat, carminised. Mount in dammar. 



(L.) The primary and secondary convolutions. The 



