GENERAL CONSIDERATIONS ON THE STRIPED MUSCLES. 175 



two extremities of unequal thickness ; the most voluminous, always turned 

 upwards, is metaphorically designated the head, the other the tail. They 

 are most frequently fusiform, sometimes conical, but rarely cylindrical, 

 prismatic or flattened into thin bands. 



" There is a particular kind of long muscles which have no analogy with 

 those of the extremities, except in their external appearance. They are 

 those which lie below, but more particularly above, the spine. Although 

 at the first glance they appear simple, yet they present as many distinct 

 fasciculi as there are vertebrae. The transverse spinoHS (spinalis dorsi), etc., 

 is no doubt an elongated fasciculus like the sartorious, etc., but the structure 

 of this fasciculus has nothing in common with that of the latter muscle : 

 it is a series of small fasciculi which have each their distinct origin and 

 termination, and only appear as a single muscle because they are in juxta- 

 position." Bichat, ' Anatomie Generale.' 



Wide muscles. Wide muscles are those which have two principal 

 axes, and are stretched beneath the skin, or around the great cavities of the 

 trunk, which they concur in inclosing and separating from one another. 

 They are elliptical, quadrilateral, triangular, trapezoid, etc. 



Short muscles. These are found chiefly around the short bones, or at 

 the periphery of the articulations which are deeply buried under enormous 

 muscular masses. Although their name indicates that their three axes offer 

 nearly the same dimensions, yet there is most frequently one, and even two, 

 which predominate. They may therefore be assimilated, in this respect, to 

 the long or wide muscles. 



D. DIRECTION. Cruveilhier has justly remarked, that the direction 

 of a muscle is one of the most important features in its history ; for 

 it allows the determination of the angle of incidence of the muscle on 

 its arm of the lever, the power of its action, and the nature of its uses. 



With regard to the direction of the muscles, we may observe : 1, The 

 form of their principal axis; 2, The relation of this axis to the plumb- 

 line ; 3, Its comparison with the axis of the bony levers which the muscles 

 surround or move. 



a. A muscle is termed rectilinear when its principal axis is straight ; 

 it is curvilinear, or circular, if this axis describes a curve more or less 

 marked ; it becomes inflected when it proceeds in a certain direction, and 

 afterwards turns on a bony or cartilaginous pulley in another direction : 

 that is to say, when its principal axis is broken into several lines. If the 

 muscle offers two axes, it will be flat or concave, these being one or the 

 other, or straight or curvilinear. 



b. With regard to the direction of the muscles to that of the plumb-line, 

 it is either vertical, horizontal, or oblique, expressions which carry their own 

 definition and require no explanation. 



c. If the direction of the muscles be compared with that of the bony 

 levers they surround and move, it will be found that they are either parallel 

 to these levers, or form with them angles more or less acute. The proper 

 direction of the bones being known, it is sufficient to indicate that of the 

 muscles to clearly establish this comparison. For instance, in saying that 

 the majority of the muscles of the shoulder are oblique from above to below, 

 and from before to behind, it is understood that these muscles are parallel 

 to the scapula, and that their incidence on the humerus takes place at a 

 right angle. 



E. ATTACHMENTS OB INSERTIONS. This is undoubtedly the most essential 

 part of the study of the muscles; for with the knowledge of their insertions 



