MUSCLE. 1383 
resemble one another in general character; some are more 
irregular, more granulous, whilst others are relatively smooth. 
The smoother ones represent cylinders, which are generally 
more or less flattened (see pl. IV, fig. 3), m which they are 
delmeated from the brachial muscles of a foetal pig seven inches 
in length, a representing the flat surface, 6 the marginal. The 
cylinder a@ presents a dark margin, and an internal clear por- 
tion, a distinction which is yet more manifest in c, where the 
dark margin is broader and sharply defined on its inner edge, 
so that it has quite the appearance of a hollow cylinder. 
I must, however, remark, that but very few fibres present this 
appearance sufficiently distinct to satisfy the mind of the ob- 
server. But in many instances it was so manifest, that no 
other explanation seemed left than to suppose the fibre a hollow 
tube. In the clear portion of the cylinder, which corresponds 
to the cavity, (in addition to some small granules,) larger oval 
corpuscles are seen, which are often very much extended in 
the longitudinal direction. Their form at once shows them 
to be nuclei, and they frequently contain one or two nucleoli. 
The distance at which they he from one another is more or 
less regular in different instances. They do not lie in the 
axis of the fibre, but eccentrically, upon and within the thick- 
ness of the wall, as is seen when the fibre rests upon its 
margin. (See the fibre 6.) That delineation exhibits a regu- 
larity in their position, since a nucleus lies upon the one side 
of the wall, the second on the opposite, and the third again 
upon the first side, and so on; such, however, does not appear 
to be the case in every instance. The nuclei are flat, for 
when viewed edgeways they have the appearance of mere 
stripes. The thickness of the wall of the cylinder seems 
to vary, as is shown by a comparison of a with c. The 
latter, c, the wall of which is the thicker, already presents an 
appearance of transverse strize. The nuclei, however, are also 
still visible in it, as well as small isolated globules which are 
contained in its cavity. Muscular fibre does not present any 
appearance of a cavity after the period of development before 
mentioned has passed, but the nuclei remain visible for a long 
time, lying in the thickness of the fibre, and often project 
upon the outside in the form of small prominences. 
The other form of muscular fibre is delineated in pl. IV, 
