1901. J TH£ MUSCLES OF THE UXGULATA. 673 



49) the posterior part of tlie muscle is suppressed, and the anterior 

 belly spreads out into fascia over the carotid artery and deep to 

 the cephalo-humeral, so that it depends a good deal on the fancy 

 of the observer whether he describes the attachment to the middle 

 cervical transverse processes through fascia, or to the deep surface 

 of the cephalo-humeral. It is apparently not an unusual thing for 

 this partial suppression of the omo-hyoid to become complete, as 

 we failed to find it in the Moulion (45) and the Fat-tailed Sheep 

 (43), and Macalister records its absence in a Chevrotain (22). It 

 is interesting to notice that in these two sheep the steruo-hyoid 

 was also absent. 



In the Tapiridse (52, 52 «) the whole muscle is present and is 

 attached to the scapula. 



In the Equidse (56, 57, 59, 61) the origin is from some part of 

 the scapula, though authorities differ as to the exact attachment 

 for instance, Chauveau (II.) says it comes from the surface of the 

 scapularis ; Owen, from the coracoid process ; and Bendz, from the 

 first rib. In any case the omo-hyoid is a very well-developed 

 muscle in the Equidae. 



Lesbres (V.) points out that in both the Euminants and Solipeds 

 the two muscles of opposite sides tend to fuse close to the hyoid 

 bone and to cover the insertion of the sterno-hyoid. "We cannot, 

 however, agree that this is always the case. 



In all the foregoing animals it will be noticed that the origin, as 

 in so many other muscles elsewhere, is the variable part, while the 

 insertion is constant ; it seems to us that this is one of those 

 examples of the dependence of structure on function, for the 

 function of a muscle is to move a certain point in a given direc- 

 tion, and it does not matter where it does this from so long as the 

 origin is in the right direction and fairly fixed. 



In the Procaviidse (67, 68, 71) the omo-hyoid is absent. 



In the Elephantidae it is also absent. 



Musdes of Ventral Surface of Neclc unconnected ivith H)foid Bone. 



Stenio-mccstoid and C'leido-mastoid. — These muscles vary very 

 much in different Ungulates. It will be seen that there is a con- 

 stantly recurring tendency to become partially inserted into the 

 lower jaw in the region of the masseter, and on this account part 

 of the muscle is often described as the sterno-maxillaris ; but this 

 practice leads to much confusion, since the name of sterno-maxil- 

 laris is also given to the forward extension of the sterno-hyoid 

 muscle to the symphysis of the jaw — an arrangement which is 

 frequently found in the Edentata, and has also been already 

 described in the Hippopotamus, <f. Sterno-hyoid. We think, 

 therefore, that it will be advisable, if possible, to limit the name of 

 sterno-maxillaris to the ventro-median muscle, which is the continu- 

 ation of the sterno-hyoid ; and if a name is required for the facial 

 insertion of the sterno-mastoid, we wou.ld suggest that of stern o- 

 massetericus (see text-fig. 86, p. 662). In the Hippopotamus the 



