MOVEMENTS OF VOLUNTARY MUSCLE. 
469 
been partially or quite deranged, so that their segments no longer conspire to form 
striae, but are visible in separate longitudinal rows, these characters are visible in the 
interior as well as on the surface, and are not lost till the focus passes beyond the 
object on the opposite side. 
It will follow from the view of the striae now taken, that they are in truth the edges 
or focal sections of plates or discs, arranged vertically to the course of the fasciculi, 
and each of which is made up of a single segment from every fibrilla. The con- 
nexions between contiguous discs, are at least as numerous as the fibrillae, and consist 
of those parts of the fibrillae which connect their segments into one thread. Whether 
these are the whole attachments, I have not yet succeeded in satisfying myself. That 
there are also special means of connexion between the segments of contiguous fibrils, 
whereby the discs are more or less compactly constructed, is very evident from the 
regularity with which the fibrillae maintain their apposition with one another ; and it 
is not a little singular that this should have attracted the attention of anatomists to 
so small an extent as it seems to have done. This is also proved by phenomena 
observable in contraction, which will be hereafter described. What these means of 
connexion may be, however, it is by no means easy to determine. My observations 
have not led me much further than to enable me to point out some examples in 
which this adhesion was exceedingly strong, and others where it was so slight, that 
all trace of striae was almost sure to be obliterated by the mere act of severing the 
fasciculi from one another. For instance, muscles in maceration present great 
variety as to the facility with which they divide into the elementary fibrils, and some- 
times their union is so intimate as to permit complete disorganization rather than 
such separation. But in recent specimens there is a similar variety even more striking 
in degree. The primitive fasciculi, by traction on their extremities, usually break off 
short, the line of fracture not appearing to pertain more to the direction of the 
fibrillae than to that of the striae ; and there is generally a slight derangement of 
both these in its immediate neighbourhood. Sometimes, however, the fibrillae project 
in considerable numbers, as a lash, from both extremities of the fracture, many de- 
taching themselves completely, and floating separately around. Here their lateral 
adhesion is exceedingly slight, and seems to be diminished by contact with water. 
The best specimens of this kind are from birds, which also afford the most character- 
istic transverse sections ; and the one fact is strikingly confirmatory of the other, for 
I conceive it to be owing to the slightness of the connexion between the fibrillae, that 
in the latter case these appear so isolated and distinct. On the other hand, it is not 
uncommon for the fasciculi to evince a disposition to split in the direction of the 
striae, so that occasionally they break off quite square, or when pulled at their ends, 
crack partially across at several points, in lines corresponding to the striae : this is 
seen in the case of the Pig (fig. 21.). Or several contiguous striae may be thus sepa- 
rated from one another, as Mr. Skey has well represented*, and as I have not un- 
* Philosophical Transactions, 1837, Plate XIX. fig. 5. 
