GENEBAL CONSIDERATIONS ON TEE STRIPED MUSCLES. 239 



A. Containing Aponeukoses. — These are layers or fascia of white fibrous 

 tissue, which envelop, in common, all the muscles of one or several adjoining 

 regions — principally those of the inferior bones of the limbs, where they constitute 

 a kind of hollow cylinder. 



The aponeuroses are formed of very resisting interwoven fibres, which are 

 attached to the bones at numerous points. At their periphery they receive the 

 insertion of one or several muscles, which keep them more or less tense. Their 

 external face is in contact with a thin connective-tissue layer that separates them 

 from the skin. The internal face sends lamellar prolongations between the 

 muscles, which enclose these in special sheaths. 



The aponeuroses maintain the muscles in their position, and sustain them 

 during their contraction. 



B. Sekous Burs^. — The serous or mucous bursae are small cavities, filled 

 with a serous fluid, which are met with at those points where the muscles glide 

 over resisting surfaces. They are generally orbicular or circular, and their interior 

 is often divided by fibrous bands. 



Their walls are formed by slightly condensed connective tissue, and may be 

 lined by a pavement epithelium ; in which case it is believed that the serous 

 bursa is produced by the simple dilatation of one of the connective-tissue meshes. 



They become much enlarged when pressure or friction is great at the points 

 where they are situated. They may appear in any region, when the conditions 

 which preside at their physiological development are accidentally produced. 



C. Tendinous Sheaths and Synovial Membranes. — Tendinous sheaths is 

 the name given to the half-bony, half-fibrous, sometimes exclusively fibrous, 

 gliding grooves in which tendons play when they are inflected to change their 

 direction, or when they glide over movable articulations. 



The tendinous synovial sheaths are serous membranes lining the tendinous 

 sheaths, and covering the tendons at the points where these two parts are in con- 

 tact. They secrete a synovial fluid quite like that of the articulations. 



When they almost completely envelop the tendon, and are afterwards carried 

 to the walls of the sheath, they are termed vaginal. 



Their walls are composed of : 1. A very fine connective-tissue membrane, 

 confounded on its external face with the tendinous sheath, by the other face with 

 the tendon. 2. A simple layer composed of pavement epithelium, extended over 

 the whole or a part of the internal face of the membrane. 



Manner of Studying the Muscles. 



A. Classification. — To facilitate the study of the muscles, two methods may be employed 

 in grouping them. The first consists in classifying them according to their uses ; describing, 

 for example, all the flexors, extensors, etc., of the same region. In the second method, the uses 

 of the muscles are not taken into account, their relations only being considered ; and they are 

 divided into groups or regions, which include all the muscles situated around a bone. The 

 latter is the method now adopted, because it is the most convenient, useful, and rational. 



B. Preparation. — We will limit ourselves to some general remarks on the following 

 points : — 



Choice of a mibject. — If there is for disposal a certain number of subjects from among which 

 it is possible to make a selection, the preference should be given to those which have the mus- 

 cular system best developed; not that large, soft, lymphatic Horses with enormous masses of 

 muscle should be chosen, for these animals are always less convenient than small or middle- 

 sized, well-bred Horses. Asses and Mules, when very emaciated, answer well for the prepara- 

 tion of the muscles. 



Position of the subject. — It is necessary to place the subject, immediately after death, in a 

 convenient position, in order that the cadaveric rigidity may set in while it is in that attituda 



