MOVEMENTS OF VOLUNTARY MUSCLE. 
473 
mencement of my inquiry, are here selected for illustration. Most have their source 
in a mere derangement of the fibrillae, whereby the striae are more or less distorted, 
or broken. Gradations of these may be seen in fig. 38, and require no comment. 
They have been described by more than one author. The usual appearance of the 
striae in a dissected state, may be best illustrated by a specimen from the heart of 
an Ox, partially affected by maceration (fig. 17-). The striae correspond in number 
with the beads, and the light and dark spaces of the one form those of the other. 
But there may be a remarkable obliquity of the striae, as in the new-born Rabbit 
(fig. 10.) and the Chameleon (fig. 14.), and as may very often be seen in the boiled 
muscle of the Crab and Lobster. I have observed that in some atrophied muscles, 
the striae are very oblique and often bent at a very acute angle in their course, pro- 
bably from shrinking of the fasciculi (fig. 28.). It occasionally happens that in some 
fasciculi, or parts of fasciculi, of perfectly healthy muscle, the striae are precisely 
doubled or tripled for a certain space, or at the same spot in different states of the 
focus. The general appearance met with is represented in fig. 19, from the neck of 
the Duck. In other specimens, where the striae have been unusually broad, and also 
thus multiplied in particular parts, I have found it to depend on the segments being 
regularly aggregated into sets of two or three, some of which showed no interval 
between their component parts, while others did so. This has been nowhere so well 
marked as in the Crab (fig. 18.)*. Another unusual appearance of the striae is dis- 
played in fig. 20, from the Staghorn Beetle. 
It seems to have been formerly the universal opinion that the transverse striae are 
in all muscles separated by equal intervals. Mr. Skey, however, has observed that 
they vary much in thickness and in number on contiguous fasciculi, and he has once 
seen them varying in size on the same fasciculus. Dr. Schwann has also remarked, 
that they vary in closeness on neighbouring fasciculi. This important circumstance 
will receive elucidation in the concluding pages of this communication, where the 
muscular motions will be treated of. At present it is only necessary to detail my 
observations as to the great variety in the number of the striae seen on fasciculi within 
a certain space. The muscle of adult animals, which has been examined after all 
contractility had ceased, will be alone alluded to. Some specimens preserved in 
spirit will be included, because I have ascertained, by direct experiment, that, when 
irritability has ceased, immersion in alcohol does not modify the size or proximity of 
the striae. 
* A doubling of the number of the transverse striae may often be seen to be occasioned by an elongation of 
the interval between the segments, as seen in fig. IS ; and I am induced to believe that in other cases an ana- 
logous appearance may depend on a progressing development of new segments, by an imperfect fission. 
3 p 
MDCCCXL. 
