136 THE ARTISTIC ANATOMY OF ANIMALS 



the spinal border. The inferior portion of its posterior 

 digitations is visible in the ox and in the horse ; these 

 digitations are less visible in the pig. They are not seen 

 at all in the dog (Fig. 68) or cat, for in these animals the 

 great dorsal muscle covers them completely. 



The great serratus muscle, by the position which it 

 occupies and the arrangement that it presents, forms with 

 the corresponding muscle of the opposite side a sort of 

 girth, which supports the thorax, and at the same time 

 helps to fix the scapula against the latter. 



When it contracts, in taking its fixed point at the ribs, 

 it draws the superior portion of the scapula downwards and 

 backwards in such a way that this bone has its inferior 

 angle directed forwards and upwards. If it takes its fixed 

 point at the shoulder, it then acts on the ribs, raises them, 

 and so becomes a muscle of inspiration. 



Because of the connections of the serratus magnus with the 

 levator anguli scapulae, some authors consider it as united 

 with the latter. But as the latter muscle is visible only 

 in the region of the neck (see p. 157), and as it is separately 

 described in man, we prefer to distinguish them from one 

 another. We shall recall the connections to which we 

 have just made allusion when describing the cervical 

 region. 



Muscles of the Abdomen 



The abdominal wall is, as in man, formed by four large 

 muscles : the external oblique, the internal oblique, and 

 the transversalis, which form the lateral walls, and the 

 rectus abdominis, situated on each side of the middle 

 line of the abdomen. This latter, because of the general 

 direction of the trunk in quadrupeds, has its superficial 

 surface directed downwards. 



The arrangement of these muscles closely corresponds to 

 that which we find in the human species. 



The External Oblique Muscle (Fig. 67, 8, 12 ; Fig. 68, 5 ; 

 Fig. 6q, 9; Fig. 70, 10). — This muscle arises, by digitations, 

 from a number of ribs, which varies according to the species, 

 the number of the ribs being itself variable for each of them, 



