Literary Notices. xlix 
Histogenesis of Myelin Sheaths.! 
In this communication Korsrer records his observations on the 
histogenesis of the myelin in nerve fibers of the central and peripheral 
nervous systems. ‘The observations were made on embryos of Salmo 
trutta and Sterna hirundo. In these embryos the Anlagen of the 
peripheral nerves consist of small bundles of very fine fibrils which 
grow from the neural canal. At their first appearance they contain no 
nuclei, but are surrounded by a sheath consisting of a single layer of 
cells derived from the mesoblastic sheath of the neural canal. The 
development of the myelin sheath begins in the large nerve fibers of 
MAUTHNER; somewhat later in the smaller nerve fibers of the bundle 
within the neural canal. At this time and during the entire period of 
the development of the myelin within the neural canal, its supporting 
tissue consists of ependym cells and their processes. The myelination 
of the fibers of the nerve roots begins at a time when there are as yet 
no nuclei in them. The development of the myelin begins therefore 
before there is present a sheath of ScHwaNnN. It begins in that portion 
of the fiber nearest the cell body and proceeds peripheralwards. Ac- 
cording to KOLsTEr the sheath of SCHWANN takes no part in the devel- 
opment of the myelin, this is an ectodermal structure as is the neur- 
axis. G. ¢) i. 
Structure of Corpuscles of Ruffini and Pacini.' 
SFAMENI gives a brief description of the different forms of corpus- 
cles of Rurrini which are found in the foot of the dog, cat and mon- 
key and then passes to a more minute description of the internal struc- 
tures of such corpuscles, which does not differ materially from that given 
by Rurrini for man. The blood capillaries follow the course of the 
nerve trunks, forming a rete surrounding the nerve fibers, but not pen- 
etrating into the interior of the terminal nerve organs. The supporting 
tissue is formed of a few elastic fibers, with much white fibrous tissue. 
The sheath of HENLE of the nerve fibers enters the outer part of the 
1Dr. Rup. KoistTer. Beitrage zur Kenntniss der Histogenese der periph- 
eren Nerven nebest Bemerkungen iiber die Regeneration derselben nach Ver- 
letzungen. Settrdge zur pathol. Anat. und zur allgem, Path., Vol. 26, 1899. 
* Relazione sulla Memoria Presentata dal Dott. PASCUALE SFAMENI: 
Intorno agli organi nervosi terminali del RUFFINI e ai corpuscoli del Pacini 
studiati nelle piante e nei polpastrelli del cane, del gatto e della scimmia. As 
della R. Accademia delle Scienze di Torino. Vol. XXXV, 1899-1900. 
