568 THE POSTERIOR PITUITARY AND THE NERVOUS SYSTEM. 



one). Since these neuroglia-fibers are deprived of myelin, they 

 cannot serve as sources of nervous energy, and merely repre- 

 sent, therefore, delicate channels through which blood-plasma, 

 obtained by them directly or indirectly from a so-called "ter- 

 minal" capillary, finds its way to the apical, or main, dendrite. 

 The conclusion which this imposes seems to us self-evident: 

 A neuron is an autonomous organ as a source of nervous energy, 

 and is supplied with blood-plasma through non-medullated neu- 

 roglia-fibrils, which are continuous with the external covering of 

 its apical dendrites. 



Are Apathy's fibrils, which, in the leech and earthworm, 

 were found by him to penetrate the cell-bodies of neurons, the 

 neuroglia-fibrils just studied? Gerlach, Haller, and others have 

 also referred to the existence of delicate nervous net-works 

 connected with the cells. The mere transformation of these 

 fibrils into plasma-channels has enabled us, we have just seen, 

 to link them with all the other elements of the function 

 studied. In other words, we simply converted the fibrils into 

 neuroglia blood-channels and found them to satisfy the require- 

 ments of the latter. Apathy found that a neuro-fibril passed 

 out of "a process of a nerve-cell": there is no fibril other than 

 the neuroglia-fiber that is continuous with the apical dendrite 

 that this neuro-fibril could represent. The neuro-fibril was 

 found by Apathy to be composed of "elementary fibrils": we 

 have seen that this is precisely the arrangement within the 

 neuroglia-fibers. He states that in their course "elementary 

 fibrillae are being given off at short intervals, until finally the 

 neuro-fibril itself may be reduced to a single elementary fibril": 

 we have quoted the statement of Professor Foster's that, as 

 regards the "fibrils of extreme tenuity," those we found to 

 act as neuroglia neurilemma, they arose "apparently from 

 the division of axis-cylinders." Finally, the neuro-fibrils, after 

 freely anastomosing in the cell-body (having entered by way 

 of the dendrite), are stated "to take their exit by way of the 

 axon." This seems to us to conclusively show, in addition to 

 the evidence adduced in the foregoing pages, that Apathy's 

 neuro-fibrils and the various net-works thought to be composed of 

 nerve-fibers by Gerlach, Golgi, B. Haller, and others represent the 

 one and same system of neuroglia-fibrils, some of which contain 



