432 
MR. E. A. SCHAFER ON THE MINUTE STRUCTURE OF 
are brought into close relation with the neighbouring ones, so that each double line of 
dots (c) no longer appears as such but as a single dark transverse band (c ; ), which 
separates the bright stripe ( b ) into two distinct parts. As these dark transverse bands 
approach one another, their bright borders encroach more and more upon the dim 
stripe (a,), until this becomes reduced to a mere line, and finally disappears altogether : 
so that in contracted (C), as compared with resting muscle, the broad dim stripes (a) 
are replaced by bright bands (bjJ, the clear stripes (b) by dark bands (c u ), these last 
being the optical sections of the disks which are formed throughout the fibre by the 
close juxtaposition of the enlarged rod-heads; the shafts of the rods have become 
much finer than before, so as to be hardly perceptible as they cross the now bright trans- 
verse bands. 
III. Transverse Section. 
When a small portion of living muscle is quickly teazed out upon a slip of very thin 
glass, to which it remains adherent, and the glass is then inverted over a ring of putty 
on an object-slide, so that the preparation is enclosed in an atmosphere which is 
saturated with moisture (Stricker’s moist chamber), we are sometimes fortunate 
enough, in examining it, to find one or more fibres which are bent upwards near the 
end, and of which consequently we get a view of the transverse optical section (fig. 3). 
Employing the No. 11 Hartnacr we observe the following: — 
The cross section of the fibre appears of a rounded or somewhat oval form, enclosed 
by a distinct contour line (section of the sarcolemma), and with a small granular mass 
in the centre (central protoplasm), which may be almost entirely occupied by one or 
more nuclei. The area of the section between the sarcolemma and the central 
protoplasm has a minutely punctuated character, this appearance being due to the 
presence of a number of minute specks scattered equally over the field ; the intervals 
between them appear homogeneous, clear, and bright. This appearance is obtained to 
whatever depth in the fibre we focus the microscope. As far as can be made out, these 
specks correspond with the rods which are seen in longitudinal view. The sub- 
stance in which they are imbedded is quite similar in aspect to that which composes 
the bright transverse disks (fig. 1 , b) ; why the dim substance in which, in longitudinal 
view, the shafts of the rods appear to be imbedded is not seen, as least as such, in the 
transverse section will become evident when we have treated of the production of the 
cross strise. 
IV. Cohnheim’s Areas. 
If, in order to obtain the transverse view of a muscular fibre, we employ the method 
recommended by Cohnheim* (that is to say, if we make a cross section of the frozen muscle 
and examine it in a so-called indifferent fluid, such as the ^ per cent, solution of salt), 
we sometimes obtain the appearance described by him of dim polygonal areas, bounded 
* “ Ueber den feineren Bau der quergestreiften Muskelfaser,” Virch. Arch. Bd. xxxiv. (1865). 
