590 



A MANUAL OF VETERINARY PHYSIOLOGY 



have reached the ground the muscles have secured control once 

 more, and he seldom falls farther than 

 his fetlocks. 



It seems quite legitimate to regard the 

 muscular union between the thorax and 

 the fore-limb as a joint. There are no 

 bones resting on each other, no synovia ; 

 but where the scapula has its largest 

 range of movement there is a remark- 

 able amount of areolar tissue, which 

 renders movement easy. The whole 

 central area beneath the scapula and 

 humerus not occupied by muscular 

 attachment, is filled with this easy- 

 moving, apparently gaseously distended, 

 crepitant, areolar tissue, over which the 

 fore-legs glide on the chest wall as freely 

 as if the parts were a large, well- 

 lubricated joint. The animal's body is 

 slung between the fore-legs, and the 

 muscle principally, if not wholly, en- 

 gaged in this important function is the 

 thoracic portion of the serratus magnus. 

 The tendinous cover to this immense 

 muscular plate imparts additional 

 strength, and is present in all muscles 

 where strain is constant or long con- 

 tinued (see p. 391). The serratus magnus, 

 on contracting, also draws the posterior 



Fig. 185.- Bones of the and u PP er P art of the scapula down- 



Fore-Leg of the Horse, wards ; this is antagonised by its cervical 



in the Attitude of portion. This muscle is a good example 



Standing. q £ a sm gi e musc i e being so arranged in 



The dotted lines show the } ts nDres that they may act together or 



whkh iP fhe m iTmb n is m kept in opposition. During the standing atti- 



rigid. tude the fibres of this muscle are acting 



1, 1, 1, The great triceps together, but in opposite directions, in 



muscle ; 2, the flexor of , , • , • A ■, n j 



the arm ; before insertion ° r <* er to maintain the scapula in a fixed 

 it gives off a slip of tendon position. During locomotion the portions 

 to the extensor of the are ac ti n e: alternately (see Fig. 188). 



metacarpus, 3 ; 4, the ex- ~,, r ° . . £ ., ^ v -, • ,-, r. 



tensor tendon of the foot ; The fixation of the scapula is the first 

 5 and 6, the flexors of the essential step towards a standing atti- 

 foot; 7 and 8 the check tude and it j s secure d by the serratus 



rampntc • r> the cucnon . m J . 



magnus, rhomboideus, and trapezius (see 

 Figs. 187, 188). The humerus below has 

 now a firm bed to press against, as the scapulae are prevented 



ligaments ; 9, the suspen- 

 sory ligament. 



