588 THE POSTERIOR PITUITARY AND THE NERVOUS SYSTEM. 



active function and govern it in the neurons with which it is 

 connected, either directly or through the intermediary of other 

 neurons. The connection with the latter would be not estab- 

 lished by continuous fibers, but through their end-bulbs, the 

 axonal of the one to the dendritic of the other, etc., in order 

 to allow of the transmission of vibratory impulses. Eeferring 

 to these larger "protoplasmic" ganglia cells, Andriezen writes: 

 "They occur abundantly throughout the gray matter, in all 

 the layers of the cortex, but are rare in the white substance." 

 Indeed, if our views are sound, the latter is a mass of axis- 

 cylinders coming from the upper strata, and surrounded by 

 their myelin, wherein energy increases with distance: a true 

 "avalanche" using Pfiuger's expression of nervous force 

 toward the lower cerebral structures. 



The predominating function of both varieties of neuroglia- 

 cell asserts itself, however, when the characteristics of the 

 cortical layers are reviewed. The first, or molecular, layer 

 contains but few nerve-cells, according to Andriezen. Its 

 proximity to the pial vessels normally suggests that, if glia- 

 cells are intermediaries between these vessels and the brain- 

 substance's circulation, they should occur in large quantities 

 in this region. "Its outermost, or superficial, region is formed 

 of a system of neuroglia fiber-cells," says Andriezen, and by 

 means of the annexed illustration, among others, he emphasizes 

 the varied directions and the length their extensions may as- 

 sume. But if the illustration on page 586 is examined, the 

 manner in which these cells (according to our interpretation) 

 are supplied with plasma may be easily understood. As shown 

 therein, the pial vessel dips into the brain-substance, sur- 

 rounded by its lymphatic membrane in such a manner, we 

 have seen, as to form two spaces, the internal of which is for 

 the blood and corpuscles to be returned by the veins to the 

 general circulation; the other, or external space, being that 

 in which the plasma for the neuroglia-cells passes after pene- 

 trating the lymphatic membrane, in order to reach the neu- 

 roglia-fibrils. This affords a supply to both kinds of cells, 

 which are seen to line the plasma-containing space. That both 

 are intimately connected with the circulation appears to us 

 beyond doubt; that the mossy, or protoplasmic, cell is endowed 



