470 
ME. a. V. ELLIS ON THE XATEEE OE THE 
or fibres. This resemblance between the two can be best demonstrated by considering 
the arrangement of the fibres when in mass, the characters of the same when separate, 
together with the length, end-attachments, and the structure of the component fibres in 
each kind of muscular substance. 
Arrangement of the Muscular Fibres. 
In both kinds of muscular tissue (voluntary and involuntary) the fibres are arranged 
after the same plan. 
In the voluntary muscles the bundles of fibres communicate freely with each other, 
producing a net-like arrangement with meshes, as in Plate XXVI. fig. 2, which represents 
this plexiform condition in the sartorius muscle of the thigh. This interweaving of the 
fibres of contiguous bundles existed in all the muscles submitted to examination, and 
muscles varying in length, breadth, and thickness were designedly selected for com- 
parison. 
In the involuntary muscular layer of the bladder the fibres form fasciculi with an 
angular outline on a cross section, and are surrounded each by a sriong fibrous sheath, 
as in the voluntary muscle. All fibres in the same stratum have the same general 
direction, either circular or longitudinal, and those of contiguous bundles intercom- 
municate often, as in Plate XXVI. fig. I, and give rise to a web with meshes. Not only 
are the adjacent fasciculi of the same stratum united in the manner specified, but the 
different strata in the wall of the bladder are joined at innumerable points, — the longi- 
tudinal fibres of one layer becoming transverse in another*. The interchanging bands 
unite in one compact whole the vesical strata ; and the same must be cut through before 
the more superficial can be detached from a deeper muscular layer. The meshes pro- 
duced by the interweaving of the fibres are smaller than in the voluntary muscle, and 
those in the deeper parts are closer or finer than the corresponding mtervals in the 
superficial layer. In consequence of this intimate interchange amongst the bundles, a 
fibre cannot be detached so readily or for so great a distance in the involuntary, as in 
the voluntary muscular tissue. 
Each bundle of fibres of the bladder is marked at short intervals by a tendinous inter- 
section more or less complete, as is the rectus abdominis muscle of the human body. 
See Plate XXVI. fig. 1, which represents some of the superficial tendinous points dis- 
sected out. These small tendons are best recognized in a contracted riscus with rather 
red fibres ; and though they are present throughout the whole muscular substance, they 
escape detection by the naked eye in the deeper layers in consequence of the general 
paleness of the texture. In some of the muscular fasciculi the tendons exist only on 
the surface, involving a few of the fieshy fibres of a fasciculus ; whilst in other bundles, 
and at other spots of the same bundle, they extend through the whole thickness. 
Where the larger bundles of fibres communicate, there is usually a tendon to be found. 
The tendinous points may be placed at tolerably regular or at different distances from 
* Transactions of the Eoyal Medico-Chirurgical Society for 1S5G, vol. xxxix. p. 328. 
