VASCULARITY IN THE NERVOUS SYSTEM 433 



is perhaps that of Aby ('99). This investigator made a careful 

 study of the arrangement and connections of the vessels in the 

 cerebellum of the cat. He found the granular layer of the cere- 

 bellar cortex to be the most highly vascular, and observed that 

 the layer of Purkinje cells was not different in its vascularization 

 from the rest of the granular layer, as it might have been expected 

 to be. He draws conclusions regarding the varying metabolic 

 activity in the different layers based upon the assumption that, 

 "at a given age, in a given organ, the relative number of blood 

 capillaries in two regions is a certain index of the relative intensity 

 of metabolic changes in those regions." This assumption may 

 be compared with the observation of various authors that, "the 

 richer any region is in nerve cells, the closer is the capillary 

 network which supplies it" (Obersteiner, '90). 



The only other point of interest in the literature which need 

 be noted is the statement of Obersteiner ('90) that, "the corpus 

 geniculatum laterale, corpus subthalamicum, and nuclei of the 

 nerves are distinguished from the other gray masses by their 

 richness in capillary vessels." 



MATERIAL AND METHODS 



The material used in this study consisted of the brains of 

 nine albino rats and one hooded rat (no. 14), which were selected 

 from among a great many preparations, their numbers being 

 12, 14, 16, 23, 24, 26, 31, 55, 56, 58. The animals were killed 

 with illuminating gas and injected with carmin gelatin by means 

 of a metal syringe, the cannula being inserted through the ven- 

 tricle of the heart into the arch of the aorta, and the thoracic 

 aorta being clamped. The brains were fixed in Bouin's fluid 

 or in 10 per cent commercial formalin (nos. 23 and 26), imbedded 

 in paraffin and cut, one sagittally (no. 12), the others transversely. 

 The sections were 20 /x in thickness in all cases except no. 16, 

 in which they were 15 ju- Only alternate sections were mounted 

 except in no. 12. The material was stained with picric acid, 

 either on the slides or in mass, the former being found best and 

 being used in all the later work. 



