298 
Analyses of Books. 
[May, 
albuminoids as the glycogen and inosite. The smooth-fibred 
muscles, which subserve the involuntary movement of the sys- 
tem, such as peristaltic motion, are next described, with the 
admission that our knowledge of their nature is as yet very 
imperfedt. 
We come now to the nervous system, described as consisting 
of fibres and cells. It is inferred that excitement in the nerve is 
due to a change in its molecular condition, and occurs as soon as 
such a change is effected with sufficient speed. 
Dr. Rosenthal then proceeds to examine a class of phenomena 
common to both muscles and nerves, in contradistinction from 
other animal organs and from the tissues of plants, i.e ., their 
regular and powerful eleCtric adtion. In three fishes —the tor- 
pedo of the Mediterranean, the eledtric eel of South America, 
and the Malapterurus electricus of the Bay of Benin — this func- 
tion of muscular and nervous tissue is intensified by special 
structural arrangements, so as to form a battery and to serve as 
an offensive weapon. It appears that every muscle, and part of 
a muscle, when at rest, is positive on its longitudinal section 
and negative on its cross section. In a regular muscle-prism 
the positive tension decreases regularly from the centre of the 
longitudinal section toward the ends ; and the negative tension 
does the same in the cross sections. During the activity of the 
muscle the differences in tension decrease. Entire muscles often 
exhibit but slight differences in tension, or even none at all. 
Nerves are positive on the longitudinal section, and negative on 
the cross section. During activity the differences in tension 
decrease. 
The question is discussed whether the muscles are irritable di- 
rectly, independent of the nerves, or only indirectly, and through 
the mediation of the nerves. The author considers this point as 
not decided, but suggests that these two classes of organs, so 
similar in most other points, may agree in irritability. 
Turning from the motor-nerves, we come to three kinds pro- 
gressively more difficult to understand — the secretory or gland- 
nerves, the nerves of sensation, and the retardatory nerves. As 
regards the process by which molecular movements in the nerve- 
cells can be translated into consciousness, Dr. Rosenthal, with 
Du Bois-Reymond, admits complete ignorance. The notion of 
Schopenhauer, who ascribes sensation and consciousness to all 
molecules, seems to him, as it does to all men of sound mind, 
but a questionable gain. Nor does he consider the question 
whether conscious conceptions can arise in the nerve-cells of the 
spinal cord as fairly open to scientific discussion. He points out 
the error of supposing that the sense-nerves are specifically dif- 
ferent and irritable, each by some definite influence alone. It is 
not, e.g ., the optic nerve, but a special terminal apparatus in the 
retina, which is sensitive to light. 
A common error is next exposed. Our sensation of light bears 
