248 PROGRESS OF MICROSCOPICAL SCIENCE. [KSSX'Tsea 
hardly evident in the other mammalia, because of the position, attach- 
ment, and the course of the fibres of the muscle. A sphincter action 
may perhaps be exercised by those fasciculi running transversely, or 
partly so, to the longitudinal tracts ; but from their weakness it must 
be very slight. Whether, and if so, how, the muscle acts on the ciliary 
processes is hardly to be determined by purely anatomical research. 
That in the dog and the cat, if it cannot move them it may alter their 
form, is not to be gainsaid ; but in the ruminants and solidungula it 
lies so far behind the ciliary processes, and its fibres take such a 
course, that a direct movement of the processes is in any case not to be 
thought of. Most important of all, Herr Flemming has found that by 
the action of the ciliary muscle the attachment of the zonula to the 
ciliary processes can be displaced backwards and forwards. 
The Comparative Histology of the type Molliisca is the title of a 
memoir by Herr Franz Boll, which forms a supplementary part to this 
fourth volume of Max Shultze's ^Archiv fur Mihroshopische Anatomie' 
Structure of the Cortical Layer of the Brain of Man. — A second 
memoir on this subject, by Herr Dr. Rudolf Arndt, is contained in the 
last number of Max Schultze's 'Archiv fiir Mikroshopische Anatomie," 
illustrated by two plates. It extends over 120 pages, but is thus sum- 
marized by the author : — (1.) The blood-vessels of the cortex cerebri, 
like those of the entire hemisphere, develop from fusiform cells, which 
are quite independent of the true nervous elements. (2.) According as 
the vessels have been formed earlier or later they are non-ramified or 
ramified. The minute vessels which in the adult pass through the 
cortex undivided, and only ramify when in the medullary layer, are the 
earliest formed vessels in the cerebral hemisphere, while all ramifying 
vessels of later stages of development belong frequently to the period 
after birth. (3.) The pia mater is not developed till a relatively later 
period (from the blood-vessels apparently), and from it are derived the 
connective-tissue corpuscles which can be unmistakably recognized as 
such in the cortical layer. (4.) The increase of the cortex cerebri 
itself takes place by the growth of the elements of the terminal fibrous 
plexus. 
On Unstriped Muscular Fibres. — By employing a very dilute 
solution of chromic acid (0 • 02 per cent.), Herr Dr. G. Schwalbe has 
succeeded in isolating unstriped muscular fibres, with their finer de- 
tails of structure preserved in such perfection as cannot be done by 
the use of any other of the known reagents. Dr. Schwalbe has more 
especially examined muscular fibres prepared in this way from the 
bladder of the dog, as being not only of large size, but easily separable 
by the above solution. Three principal parts are readily distin- 
guished in every isolated fibre. (1.) One, or generally two nuclei, 
with one or two nucleoli to each. (2.) A not inconsiderable mass of 
protoplasm accumulated about the nuclei. (3.) The contractile sub- 
stance. The usual representation of the nucleus, as staff-shaped, is not 
correct. In the fresh state it has a faintly-defined outline, is transpa- 
rent, ellipsoidal, and has no granular contents. It can be seen thus, 
for example, in the bladder of the frog, immersed in its own urine 
:5 
