546 THE POSTERIOR PITUITARY AND THE NERVOUS SYSTEM. 



nerve-fiber being merely rendered opaque, while the connective 

 tissue is destroyed. As the latter is gelatinous, its destruction 

 is easily accounted for, but why should the nerve-fiber be ren- 

 dered opaque? Evidently non-medullated fiber had been used 

 in the test, for medullated fiber is always opaque, while the 

 non-medullated is translucent. We are led to suspect, in view 

 of our belief that the axis-cylinder of a nerve contains blood- 

 plasma, that it is the latter which became opaque during the 

 boiling process. This is an important feature, for it would 

 mean that neuroglia-fibers also contain plasma. 



The identity of neuroglia-fibers as plasma-channels be- 

 comes emphasized when the morbid effects of poisons upon 

 them and upon their cells are studied. Berkley 42 found the 

 cell-bodies of the vascular neuroglia "larger, the protoplasmic 

 extensions" being "thick and knotty and the arms extending 

 toward neighboring vessels more prominent than in the normal." 

 This was noted in slides derived from animals submitted to 

 experimental acute alcoholic poisoning. When we consider 

 that alcohol primarily stimulates the adrenal system with great 

 violence and that the neuroglia closely invests the blood-ves- 

 sels, it seems permissible to surmise that the thickenings and 

 knots are dilations due to the centrifugal pressure of the plasma 

 derived from the capillaries. Especially does this seem prob- 

 able when the fact that "capillaries, like the intermediary ves- 

 sels, are tortuous and twisted" is added to the rest of the 

 evidence. And these alterations, besides an "exceeding abun- 

 dance of the polynuclear leucocytes in and around the cerebral 

 vessels," etc., are not peculiar to alcohol, for Berkley emphasizes 

 the fact demonstrated for the first time that the lesions 

 produced "are very similar to the pathological lesions produced 

 by other more virulent soluble poisons": additional proof that 

 the adrenal system underlies the morbid process. Serum- 

 poisoning was also found to cause great swelling of the bodies 

 of the vascular neuroglia, "thick groups of these swollen cells" 

 surrounding "nearly all the vessels of any size in the gray 

 layers." In ricin poisoning Berkley found the cell-bodies 

 "universally much larger than the control," and "apparently 



43 Berkley: Johns Hopkins Hospital Reports, vol. vi, No. 1. 



