COMPOSITION OF MUSCLES. 



373 



tion. When this tissue is expanded into a membrane it is termed an 

 aponeurosis ; and in this state it exists at the head or origin of the 

 muscle ; so that by tendon and aponeurosis the muscles are inserted 

 into the parts, which they are destined to move, if we except those that 

 are inserted into the skin. 



Fig. 159. * 



Compound Ventriform Muscle. 



Muscles are divided into simple and compound. The simple are 

 those whose fibres have a simi- 

 lar course and arrangement. Fig. 160. 

 They may be either flat or 

 ventriform, radiated or penni- 

 form. The compound arise 

 from different parts ; their 

 origins are, consequently, by 

 distinct fasciculi, or they may 

 terminate by distinct inser- 

 tions. Fig. 159, which is a 

 representation of the biceps 

 a flexor muscle of the forearm 

 is one of these. It has, as 

 its name imports, two heads running into one belly. It is, also, an 

 example of a ventriform muscle. 



In the pectoralis major, Fig. 160, we have an example of the radi- 

 ated muscle, or of one in which the fibres converge toward their tendi- 

 nous insertion. 



In the penniform muscle, the fibres run in a parallel direction, but 

 are all inserted obliquely into the tendon, like the feathers of a quill. 

 Fig. 161 is a representation of a double penniform muscle. Muscles 

 may, also, be complicated: that is, with one belly, and several tendons 

 having the fibres variously inserted into them ; or having several bellies 

 with the tendons interlaced. 



Fig. 161. 



Penniform Muscle. 



Double Penniform Muscle. 



They are, again, partitioned into the long, broad, and short. The 

 long muscles are situate chiefly on the limbs, and are concerned in 

 locomotion. The broad generally form the parietes of cavities : they 

 are not so much enveloped as the long by strong fibrous aponeuroses 



