A BY, Blood Capillancs in Cerebellar Coftex. 27 



Fourth. The layer of the cells of Purkinje does not appear 



to present anything peculiar as to size, number or arrange- 

 ment of vessels. 

 Fifth. The capillaries of the medullary portion are arranged 



in two ways. 



I. Elongated mesh at the top of lamina. 

 II. In the deeper portions the mesh is not elongated. 

 Sixth. Comparing the various layers. 



I. The richest plexus is in the granule layer. 

 II. A plexus is found in all parts of the molecular layer. 

 III. Capillaries are not especially abundant about the 

 cells of Purkinje. 

 Seventh. The cerebellar cortex is to be considered as a distinct 



vascular organ. 

 Eighth. Although this report is primarily and essentially a 

 record of observation, it is certainly not out of place to 

 formulate a hypothesis which may serve as a basis for fu- 

 ture work. The granule layer appears to be more highly 

 vascular than any other portion of the cortex, and the layer 

 of cells of Purkinje is indifferent. Reasoning deductively 

 from what we know of relative blood supply in other or- 

 gans, it appears fairly safe to conclude ; first, that volume 

 for volume, metabolic processes are more extensive in the 

 cells of the granule layer than in any other region of the 

 cortex ; second, that metabolic processes are not especially 

 active in the cells of Purkinje, in this particular animal. 

 This hypothesis presupposes a principle, which I will state 

 tentatively as follows : 

 Ninth. Formulation of a Principle of Histologic Angiology. 

 At a given age, in a given organ, the relative number of 

 blood capillaries in two regions is a certain index to the 

 relative intensity of metabolic changes in those regions. 

 As a corollary to the above, at various ages of a given 

 species, in a given organ or portion of an organ, the relative 

 abundance of blood capillaries is a certain index to the relative 

 intensity of metabolic changes. 



