238 SPECIAL HISTOLOGY. 



82. Accessory organs of the Muscles and Tendons. A. The mus- 

 cular envelops or fascia? are fibrous membranes surrounding single 

 muscles or entire groups of muscles, together with their tendons. They 

 differ in structure according to the degree in which they partake of the 

 character of tendons and ligaments, or of simple muscular sheaths; in 

 the one case presenting that of tendons, and in the other of membranes 

 composed of connective tissue and elastic fibres. In the former case 

 they 'are white and glistening, and exhibit, in all respects, the structure 

 of tendons and aponeuroses ; in the latter they frequently contain a 

 larger quantity of fine elastic fibres in their connective tissue, and in 

 some places may even assume the structure and dull-yellow aspect of 

 the elastic membranes (via 1 . Fig. 49), and contain a close elastic network 

 of the strongest kind. The fascia? are always of the tendinous character, 

 where for some mechanical purpose a tough unyielding structure is 

 requisite. They are of this kind, therefore: 1. At their origin from 

 bones. 2. Where muscles arise from them, and they are of the nature 

 of aponeuroses. 3. Where tendons radiate into them, and they them- 

 selves act as terminal tendons. 4. Where thickened portions of them 

 supply the place of ligaments. On the other hand, they are more or 

 less elastic where they constitute a firm envelop to the muscles, but, at 

 the same time, one which does not impede their changes in form. This 

 is their character, especially in the middle of the limbs. 



[The membranes interosseoe (forearm, leg, foramen ovale\ which are 

 not usually reckoned among the fasciae, are not apparently of the nature 

 of ligaments of the bones, but rather of intermuscular ligaments. The 

 plantar and palmar aponeuroses serve, in part, as tendons for the smaller 

 muscles of the hand and foot, but chiefly as ligaments for the retention 

 of the flexor tendons, in which respect they are analogous to the lig. cruci- 

 atum carpi dorsale, &c. In them, even in the adult, the entire course of 

 development of the nuclear fibres (minute elastic fibres), may be studied. 

 Between the fasciculi of connective tissue, straight series of 10 to 20 and 

 more, thickly placed, elliptical cells of 0-006 to 0-012 of aline, with round 



line of demarcation between the muscle and its tendon may have some connection with the 

 age and completeness of the particular bundle examined? In the Frog, we have noticed 

 that, among neighboring bundles, some exhibit transitions between the proper muscular 

 tissue and the tendon, while others have the former very sharply defined ; and the exami- 

 nation of the insertion of the triceps extensor cubiti of a seven-months' foetus has afforded us 

 the most evident transitions from tendon into muscle, although the insertion of the bundles 

 is here very oblique. The best way of expressing the mode of connection of muscles with 

 their tendons, perhaps, would be to say that the matrix of the muscle and the matrix of the 

 connective tissue, into which it is inserted, whether in the form of tendon or otherwise, are 

 invariably continuous; the appearance of continuity or of discontinuity of the two tissues, 

 arising solely from the sudden or gradual cessation of the deposit of the sarcous elements at 

 their point of junction. 



The nature of the corpuscles which are to be found at the junction of tendons with bones 

 and cartilages Professor Kolliker's "cartilage-corpuscles" has been adverted to in the 

 note at p. 97. TRS.] 



