obvious. The cells are fusiform
(spindle-shaped), have a distinct nucleus and faint longitudinal
striations (striations along their length), but no transverse
striations.

Section 97. In striated muscle extensive modifications mask the cell
character. Under a 1/4 inch objective, transverse striations of the
fibres are also distinctly visible, and under a much higher power we
discern in a fibre (Sheet 7) transverse columns of rod-like sarcous
elements (s.e.), the columns separated by lines of dots, the
membranes of Krause (k.m.), and nuclei (n.), flattened and
separated into portions, and lying, in some cases, close to the
sarcolemma (sc.) the connective tissue enclosing the fibre, in others
scattered throughout the substance of the fibre. The figure shows the
fibre ruptured, in order to display the sarcolemma; e.p. is the end
plate of a nerve (n.v.), and fb. are the fibrillae into which a fibre
may be teased.

Section 98. In the heart we have an intermediate kind of muscle
cardiac muscle (Figure 2), in which the muscle fibres branch; there
is apparently no sarcolemma, and the undivided nuclei lie in the
centre of the cell.

Section 99. Unstriated muscle is sometimes called involuntary, and
striated, voluntary muscle; but there is really not the connexion with
the will that these terms suggest. We have just mentioned that the
heart-muscle is striated, but who can alter the beating of the heart
by force of will? And the striated muscles of the limbs perform,
endless involuntary acts. It would seem that unstriated muscle
contracts slowly, and we find it especially among the viscera; in the
intestine for instance, where it controls that "peristaltic" movement
which pushes the food forward. Voluntary muscle, on the other hand,
has a sharp contraction. The muscle of the slow-moving snails, slugs,
and mussels is unstriated; all the muscle of the active insects and
crustacea (crabs, lobsters, and crayfish) is striated. Still if the student
bears the exception of the heart in mind, and considers muscles as
"voluntary" that his will can reach, the terms voluntary and involuntary
will serve to give him an idea of the distribution of these two types of
muscle in his own body, and in that of the rabbit.

Section 100. Muscular contraction, and generally all activity in the
body is accompanied by kataboly. The medium by which these
katabolic changes are set going and controlled is the nervous
system. The nervous system h