CAUSE OF STRIATION OF VOLUNTARY MUSCULAR TISSUE. 327 
naturally tend to split across in or near Dobie’s lines, as here it 
is thinnest. 
The striping of muscle can be easily explained, as shown 
before, which leads us to our final statement. A fibril is struc- 
tureless throughout its entire length, except that, perhaps, there 
may be membranes, or lines of fission, or layers of cement at 
the positions of the lines of Dobie; this we leave an open 
question. In using the word “structureless,” I must not be 
misunderstood ; structureless membranes and tissues are fast 
losing their place in histology, and once simple protoplasm is 
now most complex. What I infer is that the stripes do not 
mark the positions of alternating layers of different structure, 
the presence of which are ordinarily maintained. The compli- 
cated Muskelkistchen of the Germans does not exist. 
The muscular tissue of the heart presents many peculiarities 
which it is needless here to enumerate, for the cross striping 
alone concerns us. All those cross bands which have been de- 
scribed in ordinary voluntary muscle may here also be seen, 
and they are placed in the same relations with the turned surface 
of the fibre. The dark stripe corresponding to the crests, or 
ridges, the light bands to the depressions between them. (Fig. 7.) 
Dobie’s lines may be made out with great ease, and as there is 
no sarcolemma here, they may be accounted for also purely 
from the shape of the fibres. I have often thought that Dobie’s 
lines marked the positions of tiny ridges in the valleys, but this 
is a point more difficult to decide perhaps than in the case of 
the skeletal muscles. Transverse cleavage takes place here also 
in the thinner part of the fibre, namely, in the bright stripe, 
but whether or not exactly in Dobie’s line I have not yet definitely 
made out. 
A curious appearance, often presented by insects’ muscle, and 
sometimes also by that of the mammalia, has been described and 
figured by Mr. Schiifer. A paper descriptive of these he com- 
municated to the Royal Society of London (1873), which came 
out later on in the ‘Transactions’ of this Society, and his 
observations are published also in the eighth edition of Quain’s 
‘Anatomy.’ These have been almost entirely overlooked by 
French and German physiologists, yet in many English labora- 
tories his observations have been verified, and his conclusions 
taught. 
They are well illustrated in a representation of the muscular 
fibre of a Dytiscus, which may be seen in Quain’s ‘ Anatomy.’ 
The dark stripes are traversed longitudinally by dark rods, which 
end at both extremities in little knobs. These knobslie in the border- 
land between the bright and dark stripes. The only point which 
I would add to his figure is this, that the knobs are joined across 
