70 MR. BOWMAN'S ADDITIONAL NOTE ON THE CONTRACTION OP 



transverse strise either greatly widened and deranged {b), or altogether obliterated 

 (c, c, c), in consequence of the whole texture of the organ being broken up into those 

 primitive elements, of which the discs are constructed; and here the primitive fasci- 

 culi are frequently broken across, with or without a corresponding rupture of the 

 sarcolemraa {d, e). The extent of the swollen or contracted parts seems liable to 

 great variety ; the one selected for delineation (PI. II.) contains upwards of sixty striae, 

 but others on contiguous primitive fasciculi were more extensive. Some primitive 

 fasciculi in the neighbourhood, which at the point examined presented no rupture, 

 had a very unusual diversity in the proximity of their striae at different points, but 

 everywhere preserved, like the rest, that proportion which I have shown to obtain 

 between the diameter of the primitive fasciculi and the closeness of their transverse 

 striae. These I conclude to have been ruptured at a point further on. 



Although the bare detail of these appearances may seem to warrant the conclusion 

 that contractions have taken place in the situation of the fusiform or belly-like swell- 

 ings, the effect of which has been to stretch and even to disorganize the remaining 

 parts of the primitive fasciculi, yet I shall endeavour to confirm and illustrate it by 

 the following considerations. 



1 . The Contraction of a Muscle is the essential cause of its own rupture. 



This is best exemplified in a fragment of a primitive fasciculus of a reptile or fish 

 removed from the body, and contracting between plates of glass. The contraction 

 commences at its extremities, which, becoming swollen, receive the pressure of the 

 upper plate, and may be fixed by it. If so, the intermediate part is stretched and 

 torn as contraction proceeds ; and if an isolated contraction occurs in the centre, the 

 parts between it and the two extremities are similarly affected*, the conditions of 

 the rupture being, 1. a partial contraction of the ruptured muscle, and, 2. a force 

 superior to the tenacity of the uncontracted part, holding the ends of the fragment 

 asunder. 



The same conditions apply in the healthy living subject, where it is impossible, in 

 consequence of the admirable adaptation of mechanical arrangements to the extensi- 

 bility of muscles, that any rupture can take place solely from the action of antago- 

 nists. For example, no force of the flexors of the knee can by itself rupture the 

 extensors, because the structure of the joint prevents flexion being carried beyond a 

 point which the extensors, if relaxed, readily allow. And yet antagonist muscles may 

 and do play a conspicuous part in most muscular ruptures ; but it is only by afford- 

 ing a resistance to the approximation of the ends of the ruptured muscle, greater 

 than the tenacity of its uncontracted parts, — such a resistance, in fact, as might be 

 offered by any power mechanically adapted to produce the same effect. I say uncon- 

 tracted parts, and the propriety of supposing them in the living subject appears from 

 the examination of the tetanic muscle ; for putting aside the impossibility of any 

 rupture happening in a muscle of which no part was physically weaker than another, 



* Loc. cit., p. 490. 



