XXXI.] CEREBRUM. 355 



way. The peculiar shape of the cells in this region is best shown 

 by the "double-impregnation" method of Ramon y Cayal (p. 222). 



7. Blood- Vessels of the Cerebrum (L and H). Make rather 

 thick sections of an injected brain, and mount them in balsam. 

 They are best embedded and cut in paraffin. The whole head 

 should be injected from the aorta. 



(a.) (L) The larger vessels in the pia mater send into the cerebral 

 cortex two sets of arteries : those that perforate the grey matter 

 and proceed to supply the medulla the long or medullary arteries ; 

 and a more numerous, shorter set, that ramify chiefly in the grey 

 matter the short or cortical arteries. The grey matter is much 

 more vascular than the white, and the vessels are surrounded by 

 pori vascular sheaths (fig. 329). 



(/A) Study the arrangement and relative vascularity of the capil- 

 lary plexus in the cortex. At the surface it is less dense, and it is 

 most dense in the region of the large pyramidal cells. 



The best resume of the researches of Golgi, R. y Cayal, and 

 Kolliker is given by Waldeyer, 1 whose papers contain numerous 

 woodcuts showing not only the histological results, but their bearing 

 on physiological problems. 



ADDITIONAL EXERCISES. 



8. Cerebellum in Osmic Acid. Place very small pieces of the grey matter 

 (i unn. cubes) in i per cent, osmic acid (24-48 hours) as recommended for the 

 cerebrum (Lesson XXXI. 13). Wash in water and harden in alcohol. In the 

 sections note the medullated fibres in the granular layer, but none of them 

 pass into the outer layer of the cortex. 



9. Cerebellum in Ehrlich-Biondi's Fluid. Stain sections in this fluid as 

 directed under Spinal Cord (Lesson XXX. 13) and mount in balsam. The 

 outer grey layer and the medulla are red, the granular layer violet. In the 

 latter can be seen the two kinds of cells, one stained red, the other violet. 



10. Purkinje's Cells by Golgi's Method (p. 344). (a.) The easiest method 

 is the slow silver nitrate one (p. 344). If the preparation is successful, one is 

 rewarded by the beauty of the preparation. It is almost impossible to 

 reproduce the complexity of the processes of Purkinje's cells (fig. 330). They 

 are stained black, the nerve-fibres may or may not be stained. The sections 

 are mounted in balsam without a cover-glass. The much-branched proto- 

 plasmic processes, or dendritcs, are shown in fig. 330, A, as they appear when 

 a section is made across the lamina?, and in B when the section is in the 

 direction of the laminae. The dendrites do not anastomose with each other, 

 and all lie in one plane in the transverse direction of the leaflet. 



(b.) Fibres in Cerebellar Grey Matter. By using the rapid hardening 

 method of Golgi and Cayal many other details may be made out, but not 

 all necessarily in one section. Round the body of each cell of 1'urkinje is 

 a plexus of fibrils basket-work of fibres produced by the division or arbori- 



1 Deutsche med. WocJwnsch., Nos 44, 45, 46, 47, 1891. 



