3 ;'2 
POPULAE SCIENCE EEVIEW. 
Journal de VAnatomie. The following are some of the conclusions at which 
these savants arrive : — 1. That the respiratory oxidations take place exclusively 
in the blood, and are not limited to any particular part of its course, con- 
tinuing during the whole period of the passage of the blood from the lung 
till it arrives at the lung again. 2. That they are very active in the arterial 
system. 3. That the capillaries only augment the venous character of the 
blood by retarding its course. 4. That the respiratory processes of oxida- 
tion are progressive : that in the arterial system they are direct or indirect 
causes or consequences of reduction ; whilst in the capillary and venous 
systems they are complete, extending to the destruction of the compounds. 
Value, of Nitrate of Silver in Microscopical Inquiries. — Nitrate of silver is 
so much used by human histologists, and so much reliance is placed on 
the results it gives, that it is necessary to draw the attention of students to 
a paper read before the Vienna Academy of Sciences on the 22nd of March 
last, by Dr. Federn. The author has been engaged in studying the arrange- 
ment of the parts comprising the tissues of the capillaries. The theory that 
capillaries are formed of flattened cells joined together is foimded entirely 
upon the evidence derived from silver markings. The assertion that the parts 
mapped out by the silver markings are always each provided with a nucleus 
is incorrect. Some may often be observed to be without a nucleus ; while 
one nucleus often extends into two of these parts. The markings by silver 
are due to the crossings of winding threads, which, at least in many places, 
project near to their crossings over the outline of the vessel. With strong 
magnifying powers, two layers can sometimes be distinguished both in the 
upper and lower walls of a capillary ; and, consequently, in the whole, at 
least, three or even four layers of crossing threads. Further, two crossing 
threads of one wall of a vessel may be clearly seen to bridge one over the 
other at the point of crossing, which could not be done in the intercellular 
substance disposed cross-shaped. The author does not go further into the 
nature of these threads, but points out that from the silver reaction alone no 
definite conclusion is to be drawn, because, as we know, besides intercellular 
substance of the epithelium, the contractile substances of striped muscular 
fibres, and also protoplasm, with, perhaps, other substances, are turned brown 
by silver. 
The Rapidity of Nerve-force. — Dr. Du Bois Reymond, the distinguished Pro- 
fessor of Physiology in Berlin, and who has been recently lecturing in our 
Royal Institution, showed some interesting experiments upon the above sub- 
ject. He pointed out the analogy between nerve-force and electricity, and 
between nerves and telegraph wires, showing that the two latter are merely 
media for the transmission of their respective forces. Though the transmis- 
sion of sensations is so rapid that the effect seems to be instantaneous with 
the exciting cause, nevertheless it is not so, and there is in reality an interval 
of time between the prick of a pin on the foot and the perception of the 
sensation — an interval so minute indeed as to be inappreciable ; for no space 
of time less than the tenth part of a second can be distinguished by the 
natural powers of man. By mechanical contrivances, however, very much 
smaller portions of time can be observed and noted, and by this means, with 
the aid of electricity, the velocity of nervous agency has been determined. 
Dr. Reymond exhibited several curious and complicated experiments, in 
