236 THE ARTISTIC ANATOMY OF ANIMALS 



downwards and forwards, to terminate, after having crossed 

 the masseter, on the deep surface of the skin of the cor- 

 responding labial commissure. 



This mode of termination is the same in the ox and the 

 horse ; but where the muscle differs is at the level of its 

 upper extremity. There it ascends less than in the carnivora. 

 In the ox it arises from the zygomatic arch in the neighbour- 

 hood of the temporo-maxillary articulation ; in the pig and 

 the horse its origin is still lower, on the surface of the 

 masseter, close to the maxillary spine. 



When it contracts, it draws upwards the labial 

 commissure. 



Now, in man, we remember, it is the great zygomatic 

 that, by an action of the same kind, determines the essen- 

 tial characters of the expression of laughing. 



There is, accordingly, a connection to be established 

 between those displacements which are similar and the 

 analogy of facial expression which necessarily results from 

 them.* 



Zygomaticus Minor (Fig. 90, 4 ; Figs, 91, 92). — The 

 existence of this muscle has not been clearly demonstrated. 

 Nevertheless, Straus-Durckheim noted its presence in the 

 horse, and described it as ' a muscle arising by two heads, 

 of which one, the superior, arises from the malar bone below 

 the orbit, and passes downwards and forwards over the fibro- 

 adipose layer which supports the moustache. The second, 

 the inferior, arises from the alveolar border in front of the 

 second molar tooth, and passes forward to be inserted into 

 the same fibro-adipose layer.'f 



In connection with other quadrupeds, it is described by 

 certain authors as a very thin muscle, arising below the 

 cavity of the orbit, where it is blended with the fibres of the 

 internal elevator of the upper lip and the ala of the nose ; 

 thence it proceeds to terminate below by uniting with the 

 subcutaneous muscle. But this muscle is regarded by other 



* Edouard Cuyer, ' The ]\Iimic,' Paris, 1802. 



t H. Straus - Durckheim, ' Anatomie descriptive et comparative du 

 chat,' Paris, 1845, t. ii., p. 210. 



