286 MANUAL OF HISTOLOGY. 



though seldom, the transverse lines may become separated from one 

 another, the lateral outlines of the fibre becoming indented ; so that the 

 whole conveys to us the impression that it is about to break up into a 

 number of plates. Coincident with the more distinct appearance of trans- 

 verse striation, the longitudinal marking usually decreases in clearness. 



When treated with certain reagents the peculiarities of the tissue in 

 this case also are forcibly brought before us. Thus, acetic acid causes 

 the longitudinal lines to vanish, while the transverse remain a certain 

 time still visible. In very dilute hydrochloric acid, and also in the acid 

 gastric juice, the muscle fibre is resolved into a number of thin disks, while 

 at the same time that it swells up, and commencing solution sets in, the 

 longitudinal markings becoming completely destroyed. These disks often 

 separate from one another in the most regular manner imaginable (fig. 

 277, 4, 5). Carbonate of sodium has a similar action, but does not produce 

 swelling of the tissue ; chloride of calcium also, which, however, gives rise 

 to a shrinking and transverse wrinkling in the fibre, and not unfrequently 

 causes the appearance in its interior of transverse rents. Now, as in the 

 former cases, we believed ourselves warranted in accepting with certainty 

 the fibrillated composition of the muscle fibre, so ought we now, seeing 

 these effects produced by the chemical reagents just named, to look upon 

 the latter as made up of a number of disks or plates arranged one over 

 another (1). 



The theories broached by histologists as to this peculiar double mark- 

 ing of the muscle fibre are naturally enough very various, owing to the 

 obscurity of the subject. 



If we except a multitude of manifestly incorrect efforts at explanation, 

 there remained for many years only two modes of viewing the matter, by 

 which the nature of the texture could be interpreted, at least in its most 

 important features. Hence both of the views in question found assailants 

 and defenders. 



According to the first of these theories, already mentioned in the pie- 

 ceding section, the fibrillae are the pre-existing essential elements of the 

 fleshy mass, and remarkable for their jointed structure (fig. 277, 2). 

 Owing to the fact that the transverse markings of all the fibrillse occur at 

 the same intervals and lie one beside the other, a striped appearance is 

 communicated to the whole fibre (1). It is not difficult to see that the 

 appearances presented may be thus tolerably well explained, and why it 

 is that we sometimes remark a longitudinal and sometimes transverse 

 striation to preponderate. On the other hand, the occurrence of disks, 

 with absence of the longitudinal lines, is difficult of interpretation. 



The second theory, which has gained for itself in recent times a consi- 

 derable circle of adherents, and which we believed also, with certain modi- 

 fications, to be correct, originated with that excellent English investigator 

 Bowman. Among those who supported it, with greater or less modifi- 

 cation, the names of Harting, HaecM, Leydig, Keferstein, Margo, may 

 be mentioned. 



According to this theory, the muscle fibre consists essentially of an 

 aggregate of small particles (Fleischprismen, Fleischtheilchen), or sarcous 

 elements, which, united in a transverse direction and clinging together, 

 give the appearance of a disk or thin plate (Bowman's Disk, fig. 277, 3, 

 4, 5), and, arranged longitudinally, that of a fibril (1, 2). Both, how- 

 ever, fibrils as well as disks, it was held, are not the optical expression 

 of a pre-existing composition of the kind, which is entirely absent in the 



