196 ANATOMICAL TECHNOLOGY. 



also, the origins of tlie MM. entojyectoralis (Fig. 72) and claw- 

 trapezius (Fig. 66) are, respectively, tlieir sternal and vertebral 

 attachments. 



But the question is less easy with some muscles -which connect different parts of the 

 soma with each other, or which extend between the head and the scapula, clavicle or 

 sternum. 



Without feeling sure as to what is best, we have adopted the following basis : — 



As between the head and the neck or the trunk, the latter are more central and afford 

 origin to the muscles of the head. 



The sternum is part of the trunk, and sternal attachments are therefore origins. 



The scapula and clavicle appertain to the arm rather than to the trunk, and attachments 

 thereto, as compared with attachments to the head or neck or trunk, are insertions. 



It will be seen that the acceptance of these rules entails some apparent contradictions : 

 For example, the clavo-mastoideus (Fig. 67), like the davo-trapezius (Fig. 66), arises 

 from the skull and is inserted upon the clavicle ; but the sterno-mastoideus (Fig. 67), 

 like the splenius (Fig. 67), arises from the trunk and is inserted upon the skull. 



Hence the origin of the clavo-mastoideus practically coincides with the insertion of 

 the sterno-mastoideus. In man, where the clavicle joins the sternum, the two muscles 

 are commonly described as one, under the name of sterno-cleido-mastoideus, and one 

 part of the muscle therefore arises where the other is inserted, and vice versa. 



§ 580. The Determination of Muscular Homologies. — Of course 

 the function of a muscle depends upon its insertion, but there is 

 considerable difference of opinion as to whether the origin or tlie 

 insertion is the better guide to the determination of its homology. 

 We are disposed to assign greater morpMcal importance to the ori- 

 gin, according to the views of Barnard (^, 114). As to the value of 

 vascular and nervous supply, see Cunningham {1) and Gadow {3). 



§ 581. Fascia. — This is simply a thin sheet of the same kind of 

 fibers as the tendon, but the fibers 'may present two kinds of ar- 

 rangement. Sometimes the tendon itself is so thin as to be called a 

 fascia, or it may be continued as a thin sheet upon one or the other 

 face of tbe muscle ; in both these cases, the fibers are nearly or quite 

 parallel. The n^me fascia, however, is more often given to a sheet 

 of fibers crossing one another in various directions, and fonning a 

 sheath or covering for a muscle or a group of muscles. A fiiscia is 

 also called an aponeurosis, but the name is objectionable on account 

 of both length and etymology. 



§ 582. Forms of Muscles. — The body of a muscle may be fusi- 

 form or spindle-shaped, like that of the M. biceps (Fig. 73) ; tceni- 

 ate (strap-shaped or rihbon-liJce), as with the occipito-scapularis 

 (Fig. 67) ; fan-shaped like the subscapularis (Fig. 73) ; quadri- 



