552 THE POSTERIOR PITUITARY AND THE NERVOUS SYSTEM. 



of the neuron should be due to the same centrifugal pressure 

 that prevails in the capillaries of all peripheral structures dur- 

 ing the stage of adrenal stimulation seems undeniable. Finally 

 the fact that phenomena witnessed occur under the influence 

 of poisons in general affords the complemental evidence in 

 favor of our contention that a neuron is directly connected with 

 the circulation by one or more of its dendrites, which serve as chan- 

 nels for Hood-plasma. 



Even the haemorrhages brought on by adrenal overactivity, 

 epistaxis, haematemesis, haematuria, etc., are exemplified in the 

 engorged neuron shown in Figs. 6 and 7, and also from Berk- 

 ley's series. The observation of Apathy's, -therefore, that his 

 "cellulipetal neuro-fibrils enter by way of the dendrite, ramify 

 and anastomose freely inside the cell-body, and, then reuniting, 

 take their exit from the cell by way of the axon" finds its appli- 

 cation if, as interpreted ~by us, his neuro-fibrils are considered as 

 Nood-plasma channels. 



Still, the identity of the fibrils in the cell-body as blood- 

 capillaries has so far only been suggested by the fact that they 

 are continuous with the plasma-containing axis-cylinder and 

 fibrils. While this constitutes strong evidence, the fact that 

 they are blood-channels can only be determined by ascertaining 

 the nature of the process in which the plasma takes part. This 

 may probably be done by inquiring into the composition of a 

 neuron's ground-substance. 



THE PHYSIOLOGICAL CHEMISTRY OF THE NEURON. What 

 is the nature of the ground-substance: i.e., that between the 

 fibrils? After reviewing this subdivision of the general sub- 

 ject Barker says: "A neuron is made up, like all other cells, 

 of nucleus and protoplasm. In the latter a centrosome and 

 an attraction-sphere are present; at least it has been dem- 

 onstrated in a certain number of nerve-cells. The protoplas- 

 mic portion of the cell can be roughly divided into a periph- 

 eral exoplasmic portion and a central endoplasmic portion. 

 In neurons, as in muscle-cells, though less distinct in the 

 former than in the latter, there is a tendency to a fibrillary 

 structure, the fibrillaa tending to occur in the peripheral ex- 

 oplasmic portion of both nerve- and muscle- cells rather than 

 in the endoplasmic portion of the protoplasm. In both exo- 



