I414O ELEMENTARY BIOLOGY. [CHAP. 



a. The cell-body; composed of granular proto- 

 plasm, with a large round or oval nucleus. 

 Cf. generally with that of the unipolar cell. 



|8. The cell capsule; like that of the unipolar cell 

 but less conspicuously nucleated. 



y. The related nerve fibres, of these there are two 

 (bipolar cell): one passes straight from the 

 cell base like that of the unipolar cell; the 

 other (processus spiralis) leaves the cell at a 

 higher level, and, in passing downwards, winds 

 round the base of the cell and the straight 

 fibre. 



c. Multipolar cells. See infra § n. 

 11. The spinal cord. 



Place some pieces of the fresh cord in potassium 

 bichromate solution (2 to 3 weeks), wash well and 

 afterwards harden in alcohol of increasing strengths. 

 Stain with borax-carmine and mount in Canada 

 balsam. 



i. Examine under a low power. 



a. The cord; bilaterally symmetrical; composed of 

 a superficial lighter portion {white matter) and a 

 deeper more deeply staining portion (grey 

 matter). 



b. Nerve roots; seen as bundles of fibres running 

 out dorsally and ventrally from prolongations 

 (cornua) of the grey matter. 



c. The canalis centralis ; oval, lined by a deep 

 staining columnar epithelium. 



d. The fissures ; median dorsal and ventral, cleaving 

 the white matter only. 



