U4 FORM AND ACTION. 



named the depressores coceygis. There are likewise two other 

 muscles, one on each side, having the power of curving or flexing 

 the tail around the quarter, either to the right or left side, accord- 

 ing as the right or left muscle is in action. Altogether there are 

 eight — four pairs of — muscles belonging to the tail : two for rais- 

 ing it, two for depressing it, two for forcibly compressing it against 

 the rump, and two for curving it either on one side or the other. 

 Less than eight muscles would have proved insufficient for the 

 various movements of which the tail is capable, and with the 

 eight, admirably arranged as they are, the tail may be made to 

 perform movements in any radial direction of a circle; and, indeed, 

 by the alternate action of them, to describe a sort of circular mo- 

 tion, such as we every now and then perceive when the horse is 

 switching off flies, or making efforts to rid himself of any source of 

 annoyance or irritation. 



In the ordinary or natural manner in which a horse carries his 

 tail, the action of the muscles may be said to be nicely balanced ; 

 none are forcibly contracted — none completely relaxed — all are in 

 that semi-contracted, semi-relaxed condition, which, by physiolo- 

 gists, is characterized as their tone : and this tone is said to be 

 good or bad according as, from previous exercise and other cir- 

 cumstances, they are in a condition to do much or little work. 

 While a horse is going, the coccygeal muscles participating in the 

 general action of the body, the tail becomes partially erect ; but, 

 while in the stable, every muscle ceasing to act, it droops from its 

 own weight, and lies at rest against the quarters : and this is, in 

 truth, the only real relaxation or repose these muscles experience; 

 for, while the erectors are elevating the tail, the depressors are not 

 passively relaxed, but, like hands employed in moderating exten- 

 sion, lest the part be over-stretched, are engaged in keeping up a 

 proper degree of counter-extension. The operation of nicking 

 plainly elucidates the effects of muscular action : the depressor 

 muscles of the tail being severed, the erectors, every time the 

 horse is set in action, elevate the tail to the uttermost, and main- 

 tain it thus preternaturally erected, there being no controlling 

 powers to moderate the elevation. 



Another effect of muscular contraction well exemplified by the 

 tail, is, the prodigious force muscles aw? capable of exerting. All 



