

THE CIRCULATION OF CEREBRO-SPINAL SUBSTANCE. 575 



and lined with myelin, a feature which shows that they serve 

 for the formation of nervous energy; yet this energy is not 

 utilized in these dendrites, but by the collaterals, in addition 

 to that elaborated by their own myelin. Nor is the greater part 

 of the blood which courses through the main dendrites used 

 by them; it passes into the cell-body: a great center for the 

 production, we have seen, of nervous energy, which energy is 

 mainly utilized, not by the cell-body per se, but by the dendrites 

 and the axon through which the whole neuron's blood is con- 

 tinuously passing. 



Golgi's observation that some of the protoplasmic proc- 

 esses were connected with neuroglia-fibers and blood-vessels 

 furnishes histological proof that our interpretation of the 

 manner in which the neuron is connected with the circulation 

 is based on solid premises. The prevailing ideas, however, as 

 to the nature of neuroglia normally suggested that his views 

 included a nervous net-work as intermediary between cells, 

 neuroglia-cells being likewise considered as truly nervous 

 structures. Hence the affirmation of Cajal that collaterals 

 were totally independent of one another, especially if he gave 

 neuroglia-fibers and cells the credit of only being what they 

 are now generally thought to be: i.e., a "peculiar ground- 

 substance," in which the "blood-vessels, the nerve-cells, and 

 nerve-fibers" are "imbedded." The neuron is autonomous 

 functionally: i.e., as a nervous organ, each neuron is connected 

 with the circulation ~by its own neuroglia Uood-channels. An 

 illustration of the continuity of neuroglia-fibers with the cere- 

 bral circulation is afforded by Berkley's experiments with alco- 

 hol. "Besides the swellings in the course of the dendrons," 

 says this author, "we must always be on the watch to exclude 

 certain processes of the support neuroglia-cells that traverse 

 long distances of the cortex and exhibit a pearl-string swelling 

 in the course of the fiber." 



Are nerve-cells contiguous, as thought by Cajal? Berkley 

 states that the great Spanish investigator writes "that the 

 ascending fibers of the cortex, which have a vertical or oblique 

 course through the medu-llary layers, have their points of con- 

 tact with the protoplasm of the dendritic structures in the 

 intervals between the short transverse processes (gemmulae) 



