102 PRACTICAL HISTOLOGY. 



BLOOD-VESSELS OF THE BRAIN. 



The entire animal must be injected. Make vertical sections and mount them in dammar. 

 Observe the greater vascularity of the grey matter. 



NERVE-GANGLIA. GASSERIAN OR SPINAL GANGLIA. 



PREPARATION. With a saw divide longitudinally the head of a sheep just killed. With 

 a scalpel remove the Gasserian ganglia from the apex of the petrous part of the temporal bone, 

 and place them in the chromic acid and spirit fluid for eight days. Make longitudinal and 

 transverse sections. Stain them with logwood and mount them in dammar, or in Farrant's 

 solution. The ganglion on the posterior root of a spinal nerve of a cat or dog may be 

 hardened by the same method. 



Longitudinal Section of a Spinal Ganglion. EXAMINATION (L). Observe the sheath of the 

 ganglion within it are numerous large ganglionic cells and note their arrangement. Ob- 

 serve strands of nerve-fibres sweeping through the ganglion, and processes of connective tissue 

 passing in from the capsule into the ganglion, and supporting the cells and nerve-fibres. (In- 

 dicate ttie nerve-cells and fibres in PL XXIV., Fig. 5.) 



(H). Observe the nerve-cells, with their well-marked sheath or capsule lined with squames, 

 the nuclei of which are well-marked ; the granular mass of the cell, containing a round ex- 

 centric nucleus with an envelope, and a distinct nucleolus. It is difficult to recognise the 

 processes of the cell itself. Note the medullated nerve-fibres. 



In the examination of the transverse sections note the cells as before, but between them 

 bundles of medullated nerve-fibres cut transversely. 



It is also desirable to examine the cells from a fresh Gasserian ganglion. For this purpose 

 tease a small piece of the fresh Gasserian ganglion of a sheep in a very small quantity of salt 

 solution, and stain it with magenta solution. Details similar to those described above are seen 

 on examination, though the processes of the cells are generally broken off, and the cells them- 

 selves are frequently dislocated from their capsules. (Indicate an isolated cell within its capsule 

 in PL XXIV., Fig. 7, and without its capsule in Fig. 6.) 



GANGLIA OF THE SYMPATHETIC NERVOUS SYSTEM. 



The non-medullated nerve-fibres have already been examined (p. 45). The nerve-cells 

 of the sympathetic system have still to be considered. 



PREPARATION. Remove a sympathetic ganglion from the thorax of any animal, or pre- 

 ferably use the human superior or inferior cervical sympathetic ganglion. Harden it in Miiller's 

 fluid, or the chromic acid and spirit fluid, for four or five days, and make transverse sections. 

 Stain sections with logwood, and others with picrocarmine, and mount them in Farrant's 

 solution. 



EXAMINATION (L). Observe the capsule of the ganglion composed of fibrous tissue, and 

 notice the cells and their arrangement. Place a cell in the field of the microscope. 



(H). Observe the cell-capsule, with its included nucleated cell, which gives off processes 



