Houser, Zhe Neurones of a Selachian. 7 
haematoxylin. The scale of the work is ambitious to a degree 
bordering on superficial treatment. There are to be included 
the anatomy and histology of the brain, spinal cord, and cranial 
nerves in both the rays and the sharks. The histological de- 
scriptions usually embrace the general distribution of the nerve- 
cells of a given region, followed by exhaustive measurements 
of their sizes. His figures are hardly more than outlines of 
brain-sections, exhibiting very little detail. His most grievous 
mistake lay in his refusal to apply the brilliant generalization 
on the pallium which Rasr-Rickuarp (’83) had published 
. shortly before, rejecting it as an impossible explanation of the 
selachian forebrain. 
We now turn to the work of an investigator whose privi- 
lege it has been to lay many of the stones for the foundation of 
comparative neurology. Dr. EpincGer has demonstrated that 
it is possible to carry on research in the right way in spite of 
the exhausting cares of a physician’s life. His earlier work 
(88) includes the consideration of both the embryonic and 
adult selachian forebrain as a part of a systematic study of the 
forebrain of the several groups of vertebrates. By this time 
there had been given to neurological workers two of the most 
important methods of investigation yet imagined, the chrome- 
silver impregnation of Goel, and the myelin stain of WEIGERT. 
The former has led, ultimately, to the modern conception of 
the neurone asa structural and physiological unit; while the 
latter, including here the various modifications of the essential 
principle, has grounded our knowledge of the course of nerve- 
fibres in the cerebrospinal axis. In the research under consid- 
eration (88), EDINGER was the first .to apply the staining 
method of WEIGERT to the brain of the selachian. Using a 
counter-stain to define the nerve-cells more clearly, his results 
were characterized by a precision not known to the earlier 
workers. The chief part of the text is occupied by a descrip- 
tion of the fibre-tracts, and the drawings are evidently intended 
to illustrate this phase of the subject alone. The nerve-cells 
are described as to distribution and general external morphol- 
ogy, so far as they are made visible by the method employed, 
