228 SPECIAL HISTOLOGY. 



with alkalies. Under these circumstances the partially-swollen nuclei 

 escape, together with the fibrils, in a state of solution, from the sheaths, 

 which remain behind, and before they are dissolved may be easily exa- 

 mined in an isolated state. In many muscles, even when there are no 

 granules between the fibrils, larger or smaller fatty molecules occur 

 around the nuclei.* 



* [With regard to the vexed question of the ultimate structure of striped muscle, we ques- 

 tion if any real improvements have been made upon the description originally given by Mr. 

 Bowman (" Phil. Trans.," 1840), viz., that it consists of minute, dark, subangular particles, 

 the "sarcous elements," imbedded in a more transparent connecting substance or matrix; 

 that neither discs nor fibrils can be said to exist in the normal state, the breaking up of the 

 muscular bundle into either of these elements, resulting simply from the manner in which 

 the lines of greatest cohesion are disposed, at the time when mechanical violence is applied 

 to it. The assertion in the text that the fresh muscle of man and the mammalia does not 

 break up into discs, is decidedly erroneous as we have seen it occur repeatedly. 



Nor can we grant the invisibility of the discs in longitudinal sections of muscle : what 

 may be the case in such sections made with the double knife, we do not know, but in those 

 accidental longitudinal fractures of the muscular bundles of man, mammals, and insects, 

 which constantly occur, the edges of the discs are most distinct. Again, without making 

 any section at all, the discs may, especially in insects, be traced, by altering the focus of the 

 microscope, through the entire thickness of the bundles. The argument in the text, in fact, 

 proves too much ; for if the fibrils are visible over the whole transverse section, their dark 

 parts (discs) alternating with the light ones, must be as visible in a section, made in any 

 longitudinal plane, as they are on the surface. However, that the appearance of discs should 

 be absent in any longitudinal section of striped muscle is, to us, simply incomprehensible. 



With regard to the thoracic muscles of insects, it is to be observed, in the first place, that 

 they do not represent ultimate fibrils, but non-fibrillated primitive bundles. Dr. Auber, in a valu- 

 able paper in " Siebold and Kolliker's Zeitschrift" (H. 3 and 4, 1853), has already shown 

 that there is no defined line of demarcation to be drawn between these and the ordinary 

 muscles of insects, the two forms passing into one another by the peculiar flat bundles of 

 the Libellulidae, though he still considers the thoracic muscles to represent ultimate fibrils. 

 His sole argument, however, is their resemblance to the ultimate fibrils of the higher animals, 

 which we think loses all force, when we consider a fact that he has overlooked, namely, 

 that the muscles of the legs, &c., present a very beautiful, though very delicate fibrillation 

 the fibrils being not more than ^sootf soffotT^ 1 ^ an mcn m diameter; that is, not more 

 than from one-third to one-sixth the diameter of the thoracic muscles. Examined carefully 

 with a high power (600), with a good definition, the edges of the discs, which under a 

 lower power appeared very sharp and even, are seen to be distinctly granular, and to be 

 composed of minute, somewhat fusiform or rounded particles, not more than YofttJU* n ^ an 

 inch in diameter, distinct from one another, and imbedded in the general transparent matrix, 

 which is marked by fine longitudinal lines running between the rows of particles. Occa- 

 sionally, the broad, dark discs appear to be separated by a delicate line, and this line, if carefully 

 examined, is found to be composed of similar, but far more minute and paler particles. How- 

 ever, this appearance, though very common, is not to be met with in all the bundles. Acetic acid 

 swells the muscle up, and renders the sarcous elements still more distinct, though the whole 

 becomes very pale. If dilute ammonia be added to such a bundle, so as to neutralize the 

 acid, it resumes its original dimensions, and almost its original appearance, except that the 

 sarcous elements have often a wonderful sharpness of outline. 



The thoracic fibres, treated with acetic acid, become exceedingly pale, and the distance 

 between the discs is much increased. The latter often assume a granular appearance, but 

 not so distinctly as in the former case; nor have we been able to detect any fibrillation of 

 the intermediate substance, nor any minute sarcous elements, in them. They share the 

 former character, however, no less than the latter, with multitudes of unquestionable mus- 

 cular bundles so that taking into consideration the existence of fibrils very much minuter 



