150 THE ARTISTIC ANATOMY OF ANIMALS 



The Superior Sacro-coccygeal (Fig. 68, 39 ; Fig. 69, 34 ; 

 Fig. 70, 43). — The fascicuH which form this rnuscle 

 arise from the crest of the sacrum, and proceed thence to 

 end successively on the coccygeal vertebrae. It is in con- 

 tact in the middle line with the corresponding muscle of the 

 opposite side. 



It raises the tail and inclines it laterally ; if the muscle 

 of one side contracts at the same time as that of the other 

 the tail is elevated directly. 



The Lateral Sacro-coccygeal (Fig. 68, 40 ; Fig. 69, 35 ; 

 Fig. 70, 44). — Situated on the lateral part of the caudal 

 region, this muscle arises, in the dog, from the internal border 

 of the iliac bone and the external border of the sacrum ; in 

 the horse, it arises from the crest of the sacrum. It is in- 

 serted into the coccygeal vertebrce. 



It produces lateral movement of the tail. 



The Inferior Sacro-coccygeal ( Fig. 68, 41 ; Fig. 69, 36 ; 

 Fig. 70, 43). — This muscle, which is fairly thick, arises from 

 the inferior surface of the sacrum and the corresponding 

 surface of the sacro-sciatic ligament ; it is inserted into 

 the coccygeal vertebrae. 



It depresses the caudal appendix. 



Muscles of the Neck 



Mastoido - humeralis (Fig. 66, 3 ; Fig. 68, 9, 9, 10 ; 

 Fig. 69, 12 ; Fig. 70, 15). — One of the most important 

 muscles of the region of the neck in man is the sterno-cleido 

 mastoid. We recollect that, in its inferior part, it is divided 

 into two bundles, one of which arises from the manubrium 

 of the sternum, and the other from the inner third of the 

 clavicle, whence the denominations of the sternal portion 

 and clavicular portion. The muscle formed by the union 

 of these two portions is then directed obliquely outwards, 

 backwards, and upwards, to be inserted into the mastoid 

 process of the temporal bone and the two external thirds of 

 the superior curved line of the occipital bone. 



Now, the animals which we are here considering have but 

 a rudimentary clavicle or are entirely without it. From 



