98 PRACTICAL HISTOLOGY. 



may be observed (see Nerve, p. 42). (Indicate tlie nerve-fibres in one half and the neurogleia in 

 the other half 'of "PI. XXIIL, Fig. 2.) 



Neurogleia (H). This is the delicate framework which supports the nerve-elements fibres 

 and cells within the cord and brain. It fills all the interstices between the nervous elements 

 of the cord. It consists of a semi-fluid substance' the neurogleia matrix in which are 

 imbedded numerous very fine neurogleia fibrils, which unite to form a network. In it are 

 also found many nucleated, branched, connective-tissue corpuscles. The fibres seem to be 

 allied in their nature to elastic fibres. 



Grey Matter (H). Observe the large, nucleated, multipolar nerve-cells in the anterior Iwrn ; 

 four or five branching processes may be traced from them for a considerable distance. Each 

 cell contains a distinct spherical nucleus, enclosed in a distinct membrane and a nucleolus. 

 Round each cell is a space the lymph-space. These cells are aggregated into three groups 

 an anterior, lateral, and median. Study the posterior Iwrn, and notice that the cells there are 

 much smaller in size and fewer in number. Notice the fibrillar arrangement of the rest of the 

 grey matter, and study the substantia gelatinosa of Rolando (p. 97), which is composed of 

 a mass of neurogleia. {Indicate the anterior horn, -with its nerve-cells, in PI. XXIIL, Fig. 3.) 



Study similar sections made from the dorsal and lumbar regions of the cord, and compare 

 them with the above. Observe that the sections of the dorsal region are smaller than the 

 others. Compare the absolute amount of grey matter, and observe that it is greatest in the 

 lumbar and cervical regions. The amount of white matter is least in the lumbar and dorsal 

 regions, and greatest in the cervical. In the upper dorsal region notice a group of cells in the 

 grey matter, midway between the anterior and posterior cornua the tractus tnter-medio- 

 lateralis, 



Make similar sections of the spinal cord of an ox or man, or, best of all, that of a horse. 



It is necessary to trace the course of the fibres as seen in a section. Observe (L) the 

 anterior root of a spinal nerve. Trace some of its fibres. They enter the anterior cornu 

 of its own side, and some of the fibres pass through the anterior white commissure to the 

 anterior column of the opposite side. Others turn into the lateral column on the same side. 

 Trace the fibres of the posterior root entering as a single bundle through the substantia 

 gelatinosa. 



To study further the course of the nerve-fibres it is necessary to make antero-posterior 

 sections through the grey and white matter. This is best done in the cervical region of the 

 cord of an ox. Stain, and mount in the same way. 



Longitudinal Section of the Spinal Cord. EXAMINATION (L). Observe the grey matter in 

 the centre with a band of white matter the anterior and posterior columns cut longitudinally 

 on each side of it. Trace the vertically-arranged nerve-fibres in these, and note the some- 

 what oblique entrance of the anterior roots, some of the fibres ascending, and others descending 

 in the grey matter. In the anterior cornu note the groups of multipolar nerve-cells and also 

 the gelatinous substance in the posterior column and the entrance of a posterior root. 



TO ISOLATE A MULTIPOLAR NERVE-CELL OF THE SPINAL CORD. 



PREPARATION, (a) Dilute Potassic Bichromate. Macerate a small piece an eighth of 

 an inch long of the perfectly fresh spinal cord of an ox or sheep in a large quantity of a 

 one-eighth per cent, solution of potassic bichromate for two or three days. After this time, 

 cut out with scissors a small piece of the anterior horn, and tease it on a slide in water. Stain 

 the piece with carmine, and then continue to tease it with needles until isolated cells are 



