142 THE ARTISTIC ANATOMY OF ANIMALS 



and backwards. When tlie trapezius acts as a whole the 

 scapula is raised. 



The Latissimus Dorsi (Fig. 68, 4 ; Fig. 69, 5 ; Fig. 70, 5). 

 — This muscle arises by an aponeurosis, the so-called dorso- 

 lumbar aponeurosis, from the spinous processes of the last 

 dorsal vertebrse (the seven last in the dog, fourteen or 

 fifteen last in the horse), from the spinous processes of the 

 lumbar vertebrce, and from the last ribs. Its fleshy fibres 

 are directed downwards and forwards, being more oblique 

 in direction posteriorly, and pass on the inner side of the 

 posterior muscular mass of the arm, to be inserted into 

 the internal lip of the bicipital groove of the humerus, 

 or, a little lower down, on the median portion of the 

 internal surface of the same bone. This latter mode of 

 insertion is met with in the horse and the ox. 



The anterior fibres cover the posterior angle of the scapula 

 (as in man, where the corresponding angle, but in this case 

 inferior, is covered by the same muscle), and, a little higher 

 up, are in their turn concealed by a portion of the dorsal 

 fibres of the trapezius. It covers, to a greater or less 

 extent, the great serratus muscle. These relations are 

 similar to those found in the human species. 



We find that the fleshy fibres of the great dorsal are 

 prolonged more or less backwards if we examine this muscle 

 in the dog, the ox, the pig, and the horse. Indeed, the fibres 

 reach to the thirteenth rib in the dog and the cat (that is 

 to say, the last rib), the eleventh in the ox, tenth in the 

 pig, and twelfth only in the horse, ^^'e say ' only ' in con- 

 nection with this last because it is necessary to remember 

 that the ribs are eighteen in number on each side of the 

 thorax of this animal, and that, accordingly, the fleshy 

 fibres of the great dorsal muscle are, relatively, of small 

 extent. 



When this muscle contracts it flexes the humerus upon 

 the scapula, and helps to draw the whole of the anterior 

 limb backwards and upwards. 



There is a muscular fasciculus which, because of its 

 relations wdth the muscle we have just been studying, is 

 known as the supplementary muscle of the latissimus dorsi. 



