ON ELECTRICAL CHANGES. 603 
tions in one curve are unaccompanied by oscillations in the other, with an 
exception of no moment from point of view of question at issue. 
It is worth stating that, as two galvanometers of same pattern but of 
different internal resistance were used in the latter class of experiment, 
care was taken to change the instrument connected to either tissue during 
the course of experiment. This, however, may be looked at as of con- 
siderable advantage, and serves to make result obtained more conclusive. 
The final statement may be therefore made with positive conviction :— 
‘That the phenomena obtained in phrenic nerves are independent of, 
in the sense of being in no way due to, local changes of blood pressure or 
of circulation ; neither in so far as such conditions affect the nerve nor 
the blood-vessels contained in it.’ 
This does not affirm the absence of circumstances analogous to those 
obtained elsewhere, but places them, when present, in a position of very 
minor importance. 
The Comparative Histology of the Cerebral Cortew.—RKeport of the 
Committee, consisting of Professor GotcH (Chairman), Dr. G. 
Mann (Secretary), and Dr. F. W. Mort. 
Work upon this subject has been carried on or initiated during the year 
by Dr. G. Mann in the Physiological Laboratory, Oxford ; details are 
given in the subjoined report. 
The brains (including the retinz) of five specimens of Macaque monkey 
have been utilised for this inquiry. The material was fixed for histological 
purposes in one of the following fixatives: (a) picro-corrosive formal- 
dehyde ; (b) Zenker’s solution ; (c) Weigert’s solution of sodium bichro- 
mate, chrome alum, and formol ; (d) Weigert’s solution of chrome alum, 
glacial acetic acid, acetate of copper, and formol. All solutions were 
injected into the animal as soon after death as practicable under normal 
pressure. The Weigert methods did not yield good results, although slices 
of the cerebral tissue, 5 mm. thick, were left for five days in the solutions 
at body temperature. On embedding in paraffin and cutting sections, the 
blocks were found to be over-hardened on the surface, whilst the interior 
was insufficiently fixed. One of the specimens fixed in picro-corrosive was 
unsatisfactory, as the tissue showed extensive waxy degeneration. A 
second specimen fixed in the same way appears to give most satisfactory 
results as far as the examination of the sections has at present extended. 
Serial sections have been made of the olfactory bulb, the olfactory lobe, the 
hippocampal region, the occipital lobe and the retinz, the motor regions of 
the trunk and hind limb muscles ; sections of the motor regions of the upper 
limbs, head, &c., have not yet been made. As regards the examination of 
the olfactory bulb and the fascia dentata, it is of interest that the granules 
present in these regions, if stained by the toluidine-blue and eosin method, 
show Nissl’s substance, and thus appear to be true nerve-cells. 
The examination of the retine has brought out several points of 
interest. Sections in the horizontal plane, through the optic disc, and the 
macula lutea, show that the structure of the retin in the Macaque appa- 
rently differs from that of human retin as described by Schafer and 
Golding-Bird. The macula lies 2°75 mm. from the centre of the optic 
disc ; the outer rim of the cup measures } mm., the inner more depressed 
