70 
MR. BOWMAN’S ADDITIONAL NOTE ON THE CONTRACTION OF 
transverse striae 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 
sarcolemma ( 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. 
