CHAP. VII.] AREOLAR TISSUE OF MUSCLES. 165 



straight between two points, as in the voluntary muscles, hut twine 

 round one another, and around the organ, in a very intricate and 

 more or less spiral figure. Most of them come from the tendinous 

 cord encircling the orifices of the ventricles, and, after winding 

 through their walls, return either to some part of the same circle 

 of tendon, or end as one sort of columnar carneae in the ventricles 

 by union with the chordae tendinese. 



In the muscular coat of the alimentary canal, of the bladder and 

 uterus, the unstriped fibres are disposed, as in the heart, so as to 

 enclose a cavity, but without having, as in that organ, any point at 

 which they can be said to commence or terminate. In the alimen- 

 tary tube they are arranged in two laminae, the respective fibres 

 of which take a course at right angles to each other. In the 

 bladder the arrangement is reticulate. The elementary fibres form 

 sets of variable thickness, which at numerous points send off de- 

 tachments to join neighbouring bundles, whence has sprung the 

 notion that the fibres are branched. It is manifestly, however, the 

 sets of them only that are branched; the unstriped, like the striped 

 fibres, being invariably simple from end to end. In the uterus the 

 disposition of the fibres is essentially similar, calculated to allow of 

 great variety in the capacity of the cavity they encircle. 



Of the Areolar Tissue of Muscles. This tissue is much more 

 abundant in the voluntary than in the involuntary muscles. To the 

 former it gives an external investment, which sends septa into the 

 intervals between the larger and smaller packets of fibres, and 

 thus enables them to move in some degree independently of one 

 another. The density of these general and partial sheaths is pro- 

 portioned to the amount of pressure to which the organ may be 

 subject, as is exemplified in the superficial muscles of the back, 

 and in those superficial muscles generally where a fibrous aponcu- 

 rosis does not exist. The areolar tissue does not usually clothe 

 every individual fibre from end to end, giving it a cellular sheath, 

 except in cases where the elementary fibres are of large dimensions. 

 The areolar tissue, besides affording protection to the muscular 

 fibres, admits of motions between them ; and, by forming a con- 

 necting bond between neighbouring bundles, it must also serve the 

 important office of limiting undue motions of one part of a muscle on 

 another part. But a principal use of it appears to be that of fur- 

 nishing a resisting nidus in which the delicate vessels and nerves 

 can traverse the interstices of the fibres, and by which they can be 

 protected from hurtful dragging during the unequal and oscillat- 

 ing movements of the fibres of a voluntary muscle in its state of 



