Reviews and Records in Anatomy and Physiology. 97 
ment of the discs, anomalous appearances in the fibrilla which, 
although regular, are undoubtedly due to some abnormal changes 
occurring in the elastic substance of which the fibrilla or even its 
discs are composed. Several of these curious aspects have been 
described and figured by Mr. Dobie in his paper above cited. 
Thus, in some cases, instead of the appearance of a regular suc- 
cession of square blocks which appear white, while the line of 
their apposition appears dark,—presenting, on the whole, a kind of 
tape-worm appearance,—there is observed another dark line bisect- 
ing the light space. There are then seen, broad dark line (the 
line intervening between the discs), light space, narrow dark line 
(line bisecting the disc itself ), light space, and, broad dark line 
again. In other cases, the broad dark line is as wide as the disc 
itself, and then there appears a regular succession of light and 
dark spaces of equal width —the light spaces being bisected by a 
dark line, and the dark ones by a light line. But this beautiful 
series of light and shade may be completely reversed by a change 
of focus. In some rare instances, one of which we have now 
under observation, these light and dark spaces are quadrisected 
instead of bisected, there being two light or dark narrow lines 
instead of one across each space. 
These singular appearances, of which there are numerous other 
Varieties, might perhaps be accounted for on the supposition that, 
from rough handling, changes have occurred in the constitution 
of the component substance of the fibrilla, which produce the 
refraction of the light here observed. But we will add that in all 
the examinations we have made of this interesting point, we have 
seen nothing in these varying aspects leading us to doubt the true 
dise-composition of the fibrille 
Another point to which we would here refer as at least of some 
suggestive interest, is the question whether the fibrille: are inves- 
ted with a sheath or not. Until quite recently we have observed 
nothing indicating that such sheath exists; but in some lately- 
prepared specimens, not only the disposition of the discs compos- 
lng the fibrilles, to each other, but also a kind of crenulated or 
denticulated aspect of the edges of the fibrille, sometimes ob- 
served ;—such phenomena might be well explained on the sup- 
position of the presence of a sheath, but, at the same time, they 
by no means demand this supposition. Jn some instances they 
have a striking appearance, but it is possible that they may be the 
remains of that gelatinous substance which binds the fibrille 
together in a fibre.* 
* Dobie speaks of a homogeneous, delicate membrane, which is sometimes ob- 
Served stretched between two fibrille when they are separated at a greater or less 
acute angle from each other, resembling the web between the toes of a 
bird. It may be the same substance that we have observed. See loc. p. 114, 
Pl. vu, fig. 8, a, b. ; iy a 
Szconp Serres, Vol. XVII, No. 49.—Jan, 1854. 13 
