^^SioSt'^S?] PBOGKESS OF MICROSCOPICAL SCIENCE. 213 
end of the cell tapers gradually into a straight process, which runs 
directly toward the surface of the convolution, and may be traced to 
a surprising distance, giving off minute branches in its course, and 
becoming lost, like the others, in the surrounding network. Many of 
these cells, as well as others of a triangular, oval, and pyriform shape, 
are as large as those in the anterior grey substance of the spinal cord. 
In other convolutions the vesicular structure is again somewhat 
modified. Thus, in the surface convolution of the great longitudinal 
fissure, on a level with the anterior extremity of the corpus callosum, 
and therefore corresponding to what is called the superior frontal 
convolution, all the three inner layers of grey substance are thronged 
with pyramidal, triangular, and oval cells of considerable size, and in 
much greater number than in the situation last mentioned. Between 
these, as usual, is a multitude of nuclei and smaller cells. The inner 
orbital convolution, situated on the outer side of the olfactory bulb, 
contains a vast multitude of pyriform, pyramidal, and triangular cells, 
arranged in very regular order, but none that are so large as many of 
those found in the convolutions at the vertex. Again, in the insula, 
or island of Keil, which overlies the extra-ventricular portion of the 
corpus striatum, a great number of the cells are somewhat larger, and 
the general aspect of the tissue is rather different. A further variety 
is presented by the temporo-sphenoidal lobe, which covers the insula 
and is continuous with it ; for, while in the superficial and deep layers 
the cells are rather small, the middle layer is crowded with pyramidal 
and oval cells of considerable and rather uniform size. But not only 
in different convolutions does the structure assume, to a greater or less 
extent, a variety of modifications, but even different parts of the same 
convolution may vary with regard either to the arrangement or the 
relative size of their cells. 
Between the cells of the convolutions in man and those of the ape- 
trihe I could not perceive any difference whatever ; but they certainly 
differ in some respects from those of the larger mammalia — from 
those, for instance, of the ox, sheep, or cat. 
The Structure of the Human Blood-corpuscle. — As far back as May, 
1868, Professor Freer, of Rush Medical College, U.S., asserted that 
human blood-corpuscles were not, as heretofore supposed, simply 
bi-concaye discs ; but that, on the contrary, there may be seen (by the 
use of Wale's illuminator) a nipple-like eminence in the centre of the 
concavity of each well-formed disc. This papillary eminence is about 
TWO 0" mch in diameter at its base ; consequently, he arrays 
himself against the expressed opinion of physiologists and microscopic 
anatomists as set forth in standard works, to wit, that the human blood 
is non-nucleated. Continued investigation on this subject since the 
first article was published, has confirmed the announcement then 
made, and now he illustrates his discovery by two diagrams — one 
representing corpuscles of human blood, the other corpuscles of a 
frog — ^both of which exhibit these eminences. All of the research 
upon which his present convictions are based has been prosecuted by 
the use of reflected light instead of transmitted light, by which most 
examinations of blood-corpuscles have been made heretofore. Cor- 
