MAMMALIA. 661 



too, this muscle exists, but under a very different aspect ; being 

 only found in certain regions of the body, where it forms nume- 

 rous cutaneous muscles adapted to different offices. In the 

 neck, where it is principally developed, it is called the platysma 

 myoides : in the facial region it is likewise of great importance ; 

 the occipito-frontalis, the corrugator supcrcilii^ and other mus- 

 cles connected with the expression of the countenance, being indu- 

 bitably but portions of the fleshy pannicle. In the palm of the 

 hand it is slightly visible, forming the palmaris brevis ; and even 

 the little muscles connected with the external ear may be referred 

 to the same series. 



(743.) In Whales no pelvis or posterior extremities exist ; it is 

 needless, therefore, to remark, that the whole of the muscular 

 system appropriated to those parts in higher animals must be 

 totally wanting : but, in return, the muscles connected with the 

 caudal portion of the spine are amazingly powerful, so as to render 

 the horizontally expanded tail an instrument of propulsion, ade- 

 quate to the necessities of these unwieldy animals. A large tri- 

 angular muscle is found in the CETACEA, apparently replacing the 

 quadratus lumborum, the psoas, and the iliacus, which arises from 

 the lower surface of the last rib, from the last dorsal vertebra, and 

 also from those of the loins and sacrum : from this powerful assem- 

 blage of muscular fasciculi tendons are given off, to be inserted 

 into the lower surface of the bones that support the tail, converting 

 this organ into a mighty oar, adapted by its position to bring the 

 creature with all speed to the top of the ocean in search of air. 

 It is, as might be supposed, in the muscles of the limbs that the 

 most important differences exist. In the anterior extremities, for 

 example, the presence or absence of a clavicle will materially affect 

 the disposition of the muscles of the shoulder, as will also the ex- 

 istence of a coracoid process to the scapula ; nevertheless in their 

 general arrangement they conform to those of Man. The rhom- 

 boid muscles, which to creatures walking on all fours must be im- 

 portant agents, are generally found in quadrupeds to take their 

 origin as far forward as the head ; the serrati magni likewise, 

 whereby in the prone position the weight of the body is as it were 

 suspended from the scapula, must be immensely strong. 



The muscles acting upon the arm are similar in all the Mam- 

 malia; but in the fore-arm, as might be expected from the very 

 variable condition of this part of the skeleton, the disposition of 

 the muscular system varies too, and even the existence of many 



