MOVEMENTS OF VOLUNTARY MUSCLE. 
483 
oval or circular discs, frequently concave on one or both surfaces, and containing 
somewhere near the centre, one, two, or three very minute dots or granules (figs. 39. a. 
40. a. 51. a., &c.). This at least has been their most common form, when they have 
seemed most entire and free from injury. It is also their general shape when 
discernible, as occasionally happens, without chemical treatment. But they present 
some varieties in figure, being sometimes thick or elongated, or curved and irregularly 
oblong, at others of indefinite shape and granulated aspect. It is doubtful, however, 
how far those having such characters are modified by the circumstances of the exa- 
mination. I have witnessed the breaking down of the more regular ones into a gra- 
nulated mass, in repeated instances, on the addition of acid, by the forced elongation 
of the fibriilee, among which they lie (figs. 39. 4 7-), and am therefore induced to think 
such specimens to be generally misrepresentations of nature. If they be not always 
fallacious, they may be regarded as an indication of a deposit and absorption of suc- 
cessive crops of corpuscles. These bodies are usually numerous in proportion to the 
size of the fasciculus, so that as a general rule equal masses have about equal numbers ; 
but this is liable to some exceptions, as the same fasciculus may sometimes have them 
crowded in one part and more scanty in another. Where the fasciculus is small, as 
in Birds and Mammalia, they lie at or near its surface, but in contact with the fibriilee, 
within the sarcolemma. This is clearly shown by bringing into focus different por- 
tions of the fasciculus in succession, under high powers, as well as by a corpuscle 
occasionally adhering to the sarcolemma when separated by fluid from the surface of 
the fibriilee. But in proportion as the fasciculi assume a greater bulk, the corpuscles 
are found to be diffused more uniformly through their substance, and may be every- 
where traced by a moving focus. This is especially the case in Reptiles and Fish, in 
which I first met with them, and where they are at all times the most convenient for 
observation*. In the Insects that could be most readily obtained, and which have 
been submitted to examination, they are usually disposed with more symmetry, either 
singly or in pairs, along the central axis of the fasciculus (figs. 53. 54. 70. 73.), an 
arrangement occasionally observable in Reptiles (fig. 46.), and which affords an im- 
portant insight into their essential nature. In one instance (in the Chrysalis of the 
Tiger Moth, fig. 55.) a number of corpuscles similar to these were observed on the ex- 
terior of a fasciculus, but their relations are doubtful. These corpuscles have mani- 
festly some adhesion to the fibriilee with which they are in contact, since they are 
influenced by their movements (figs. 39. 47. 85.), and generally retain their connexion 
with them, when these are torn asunder from one another (fig. 49.). Some, however, 
often become detached, and float in the fluid by which the object is surrounded, 
thereby evincing their existence as independent parts. They lie among the fibriilee, 
but so attenuated is their form, that they do not derange the striee. Sometimes, 
indeed, a dark longitudinal streak may be observed, extending on either hand from 
* Their dispersion among the mass of fibrillse is well seen in a transverse section from the Skate (fig. 3.), 
but in general they are not thus visible. 
3 q 2 
