1038 General Notes. 
from the hinder portion of this cells, are cut off, which wander in 
and join the “ yolk cells.” but have nothing to do with the forma- 
tion of the mesenteron. The remainder of the primary entoderm 
differentiates into two large lateral and a middle solid longitudinal 
and, and in the former there appears in each segment a cavity. 
The outer wall of this cavity forms the somatopleure, the inner 
the splanchnopleure and epithelium of the digestive tract. This inner 
wall soon separates completely from the outer in the middle line, 
and there becomes two-layered, thus developing both entoderm and 
splanchnopleure. These lateral bands of entoderm now unite with 
the middle one and soon enclose the whole yolk and the “ yolk 
cells” which latter later degenerate and are absorbed.—J.S. K. 
MICROSCOPY." 
VITAL INFUSION or Nerves WITH METRYL-BLUE.—Prof. 
Ehrlich’s? experiments in staining nerves with methyl-blue, mark the 
second great advance in staining living tissues. The discovery ot a 
veritable nerve-stain, that acts intra vitam, has already led to the 
settlement of many disputed points, and promises to furnish a 
means for deciding the problem of nerve-endings. The well-known 
color-reaction induced in newly formed bone-substance as the result 
of madder-feeding, is outshone by this wonderful reaction between 
methyl-blue and the axis-cylinder. l 
According to Ehrlich two conditions are necessary in order to e 
the methyl-blue reaction : These are (1) saturation with oxygen an 
(2) alkaline reaction. The first condition can be secured only be 
free exposure of the object to the air. If a cover-slip is used, the 
air is thus excluded, and the stain rapidly disappears. 
As to the second condition, it is known that nerves at rest have 
an alkaline reaction. It is necessary, therefore, to experiment re 
resting nerves. The state of rest may be forced by severing ‘ 
nerves before infusion with methyl-blue, or by poisoning the animals © 
with curare. The nerve-endings of the retina may be studied me 
animals that have been kept some time in the dark before infusio ; 
The number of nerve terminations that stain under ordinary ae 
ditions is, however, so great, that a wide field for histological aie 
tigation is open to us without having recourse to the expedients J 
mentioned, se 
1 Edited by C. O. Whitman, Director of the Lake Laboratory, Mi 
waukee. Pres 
* P, Ehrlich. Ueber die Methylenblaureaction der lebenden Ner 
substanz. Deutsch. med. Wochenschr., 1886, No. 4. 
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