cxl Journal of Comparative Neurology. 



degenerating medullary sheath leaves a fluid in the sheath which is grad-. 

 ually absorbed. There is not a fatty degeneration of the medullary 

 sheath, though infiltration of fat in adjacent structures cannot be denied. 

 Neither is there a chemical transformation in the sense of Neumann and 

 Eichhorst. Leucocytes have nothing to do with the degeneration, and 

 Ranvier went too far in ascribing it solely to the proliferation of the nu- 

 clei. The axis cylinder decomposes before the meditlla and sheath. The 

 degeneration passes with' marvelous speed from the site of injury periph- 

 erad. 



The proliferating nuclei of Schwann's sheath seem to facilitate the 

 degeneration and regeneration, but neither they nor the increased proto- 

 plasm have anything to do with the formation of the axis cylinder. 

 Biuiger's protoplasm bands are probably simply folds in Schwann's 

 sheath. There is no reason to doubt the statements of Koelliker as to 

 the consistency of the axis cylinder and the connective nature of the 

 sheath. The axis cylinder grows from the central stump continuously. 

 The new fibres appear in 8 or lo days. In some cases the medullary 

 sheath is not at once formed. Nerves caused to degenerate by crushing 

 do not form more than a single fibre in a sheath. The new Schwann's 

 sheath is apparently formed by the nuclei of the old sheath. 



To judge from the drawings there is mucli reason to suspect that a 

 better interpretation would show an intimate connection between the nu- 

 clei of .Schwann and the axis cylinder, which latter is jointed in a way 

 suggestive of moniliform concresence. 



The Ckkkbri'm of Reptiles. i 



This extensive paper by a young physician recently Americanized 

 contains promise of good work, but fails of adding materially to our 

 knowledge by reason of ignoring previous writers and the crude methods 

 emploved. The terminology is that of Edinger. Brains hardened in 

 Mueller's fluid and stained with analine cannot be expected to yield his- 

 tology. The differentiation of cells seems to have beeu imperfect, but 

 the difference between the pyramidal and fusiform cells of the various 

 areas were made out. Although special attention is given to the snake 

 brain we find no mention ef the remarkable peculiarities of the tuber 

 with its lateral pero and olfactory fossa and no recognition of the relation 



I. Meyer, A. Ueber das Vnnlerliirii oinigor Reptilion. Zcilscli. f. wiss. ZooL 1 



