352 



PRACTICAL HISTOLOGY. 



[XXXI. 



brain of a small animal. In the case of a human brain, select the 

 ascending parietal or ascending frontal convolution. Make V.S. 

 either by freezing or in paraffin after staining in bulk in borax- 

 carmine. Other sections may be stained in aniline blue-black, and 

 all are mounted with balsam. 



"With the naked eye observe the shape of the convolution, the 

 grey matter outside, of a certain thickness (y^-i in. thick), and 

 deeply stained, and inside it the white matter less deeply stained. 



(L and H) (a.) Observe the white matter, composed of medul- 

 lated fibres, with leucocytes here and there between them. 



(b.) Outside this the grey matter, composed of several layers, 

 recognised by the arrangement and shape of the cells present in it. 



FlG. 3 2 7- y.S. of Cortex of the 

 Ascending Frontal Convolution, 

 i.e., a Motor Area. Carmine, 





FlQ. 328. V.S. Middle Frontal 

 Convolution. Carmine, x 20. 



It will depend very greatly upon the plane of the section whether 

 the student sees all the layers in any single section. They are 

 usually in a five-layer type, but the relative thickness of the layers 

 varies in different parts of the cerebrum. 



A. Arrangement of Nerve-Cells. 



(c.) The layers from the surface inwards are : 



(i.) The narrow outer or first layer (or finely-granular or mole- 

 cular layer) consists of a network of fibrils with a very few small 

 cells. Chiefly neuroglia cells, mostly vertical to the surface. 



By Golgi's method, it can be shown to contain a layer of medul- 

 lated fibres just under and parallel to the pia, and also some 

 branched non-medullated fibres. It also contains a few small 

 nerve-cells with two or more axis-cylinder processes. The latter 

 details can only be detected in a preparation made by Golgi's 



