1:20 MUSCULAR SYSTEM. 



Actioti. — To flex or writhe the back upon the withers; and to 

 aid in the erection of the neck. 



SEMI-SPINALIS DORSI. 



Situation. — Deep-seated, upon the back. 



Fortn. — Half-penniform ; elongated ; curving with the spine. 



Attachment. — Posteriorly, to the sacrum, underneath the pos- 

 terior spine of the ileum ; to the articular processesof the lumbar ver- 

 tebrae, and the transverse of the dorsal : anteriorly, to the lumbar 

 spines, and those of the back ; extending forwards to the withers. 



Relations. — Deeply buried underneath the longissimus et spi- 

 nalis dorsi,and lying close upon the lateral parts of the spine of the 

 back and loins. 



Direction. — Oblique, from below upwards, and from behind 

 forwards : the obliquity of the packets increasing from behind to 

 the front. 



Structure. — Consistingof a regular series of small fleshy packets, 

 intersected with broad thin portions of tendon, which increase 

 in length with the dorsal spines. The posterior packets are 

 mostly fleshy in substance ; but the anterior present several long 

 flat tendons, distinct from the other parts, which are fixed to the 

 spines of the withers. 



Action. — To co-operate with the longissimus dorsi in pro- 

 ducing a more complete flexion of the back. 



DIAPHRAGMATIC REGION. 



Containing only the single muscle from which it takes its 

 name. 



DIAPHRAGMA. 



Situation. — It forms the fleshy and tendinous partition divid- 

 ing the cavity of the chest from that of the abdomen. 



Form. — Broad, circular; flattened from before backwards; 

 anterior surface, convex; posterior, concave: bifurcate, superiorly; 

 having two elongations or appendices extended backwards, and 

 terminating in pointed extremities. 



Division. — The broad circular portion is sometimes distin- 

 guished as the greater muscle ; wiiile the appendices or crura 

 are said to form the lesser. 



Attachment. — The greater muscle is attached by fleshy digita- 

 tions to the cartilages of the eighth ptiir of ribs, and to those of 

 all the posterior ribs, with the exception of the two last; also to 

 the ensiform cartilage. Of the appendices, the right, the longer 

 one, is attached to the bodies of all the lumbar vertebree ; the left, 

 or shorter one, has separate tendinous attachments to the first 



