xviii JOURNAL OF COMPARATIVE NEUROLOGY. 
fibril arising from it. Rurrini has illustrated his minute description 
with seven figures, showing the varicose ultraterminal fibril, the fine 
collateral branches, the different modes of termination of the fibril and 
the long smooth secondary fibril, concerning the termination of which 
he is in doubt. APATHY, in discussing these observations of RUFFINI, 
dwells upon their importance as showing in a concrete case and that in 
man, that some of the supposed nerve terminations are not terminations, 
and that they may constitute a direct connection from one neurone to an- 
other. Comparing these results with those gained by himself in his 
work on neurofibrils, he believes that there are no natural nerve termina- 
tions; that the conducting path is continuous and comparable to the 
circulatory system. DR. DE WITT. 
Hi stogenesis of Schwann’s Sheath. 
In trying to stain the neurofibrils in the developing axis cylinders 
of embryos after the method of Apatuy (gold chloride method), Gur- 
wItscuH found that, while the neurofibrils were not stained, the sheaths 
of SCHWANN (neurolemma) were stained, at a time when other known 
methods did not show their presence. His observations were made on 
the sciatic nerves of sheep embryos, removed at a time when the nerve 
fibers possessed as yet no medullary sheaths. At this stage the sciatic 
nerves consist of a number of secondary bundles, surrounded by a 
loose connective sheath, concentrically arranged, and each bundle is 
surrounded by a delicate sheath containing large nuclei. In cross-sec- 
tion the secondary bundles appear finely granular and contain few 
nuclei. A cross-section of such a nerve, stained after APpaTHy’s gold 
method, shows the delicate sheaths of the secondary bundles stained a 
deep violet, nearly black, from which lamella-like processes pass into 
the interior of the bundles, similarly stained. The nuclei in the sec- 
ondary bundles are associated with these lamalle. Longitudinal and 
cross-sections of suitable stages show that the lamallz above mentioned 
develop into tubular structures—the sheaths of SCHWANN. 
The sheaths of SCHWANN are, therefore, of mesodermal origin, 
developed from mesodermal cells with lamellar processes. The close 
apposition of the sheath of Schwann and the medullary sheath is 
attained secondarily by the increase in thickness of the axis cylinder 
and the medullary sheath. G. Cae 
1 Dr. ALEXANDER GURWITSCH. Die Histogenese der Schwann’schen 
Scheide. Archiv fiir Anat. und Phys. Anat, Abtheil., Heft 1 and 2, 1900, 
