Aby, Blood Capillaries in Carbellar Cortex. 3 1 



into capiliaries in the granule layer ; and third, a set of capil- 

 laries distributed immediately through the molecular layer. 

 For the sake of clearness and brevity, I propose here to desig- 

 nate these by the letters A, B and C. These are arranged in 

 order in the summary. 



In the plate, which is produced by photographic processes, 

 from the section itself, examples of these three types may be 

 seen. At i, 6, 10, 11 and 13 are examples of class A. At 

 2, 9 and in various other situations, examples of class B, 

 Above the X to which lines 4 and 7 lead are examples of 

 class C. 



It is to be clearly understood now that no sharp line separ- 

 ates these three classes. The classes merge one into another, 

 and frequently it is difficult to assign a given vessel to its proper 

 class. By a careful study of the plate there will be observed in 

 several situations vessels which may be classed as either B or 

 C. Such a study will also demonstrate that not much reliance 

 can be placed on sise as a basis of classification. As to the rel- 

 ative nnvibos of vessels of these three classes, it is possible to 

 arrive at only a rather indefinite approximation. The average 

 of a number of enumerations show the following rates. One 

 vessel of class A to about twenty vessels ot class B, and one 

 vessel of class B to about fifteen of class C. 



Considering the arrangement of vessels in the various lay- 

 ers of the cortex, we may state the proposition that the granule 

 layer \\z.'~, four sources of blood supply. An arteriole of class 

 A may be seen to pass into the medullary layer, and at a greater 

 or less distance from its point of departure from the granule 

 layer, send a recurrent branch to the granule layer of its own 

 side. In the plate, this may be seen at i and 11. But the 

 greater part of its blood supply is derived from vessels of class 

 B. Numerous instances of this may be seen in all parts of the 

 plate. But if all the vessels of class B, should become obliter- 

 ated, and all the recurrent branches from class A failed, still 

 the granule layer could receive a supply of blood from the anas- 

 tomosing capillaries from class C. This anastomosis may be 

 studied by means of a magnifier in various parts of the plate. 



