THE HORSK IN MOTION. 33 



they are attached, and not sufficient attention has been given to their 

 action in correlation to the others with which they are coworkers. 

 The forces employed in each limb, considered alone, are very complex. 

 The same muscle may be an extensor at one time and a flexor at an- 

 other in the same stride, as we shall show further on. 



In order to enable the reader to understand the muscles and their 

 relations without too great a tax on the powers of abstraction, the ser- 

 vices of Mr. William Hahn.a Diisseldorf artist, were secured to delineate 

 the most important muscles as they were exposed in dissection ; but no 

 skill can do justice to the nacreous tints of the tendinous envelopes 

 of the deep muscles. With all the aid which art can render, the 

 complicated mechanism of the horse cannot be presented by written 

 description in such a manner as to dispense with a little close attention. 

 A perfect familiarity with the subject, so as to enable one to carry 

 the plan of the whole machine in the mind, can only be attained by the 

 aid of dissection. A knowledge of the construction of the machine 

 is imperative upon one who would comprehend its action. It is 

 as necessary as for an engineer to understand the construction of his 

 engine. With that knowledge one can understand the elements of a 

 horse's strength and speed, analyze his movements, and appreciate the 

 source of the danger from injury in great trials of speed. 



Let us first review certain physiological and general anatomical 

 facts, well, but not so generally known, as could be wished. The me- 

 chanical parts divide themselves into two classes, the active and pas- 

 sive. The passive parts are the bones and ligaments ; the active parts 

 are the muscles in which dwells all the power. 



Of the bones it may be said, in general, that they are the levers on 

 which the muscles act, and by means of which their power is made 

 available ; their form depends upon the uses which they are designed 

 to serve. When intended for bases of action, they are thin, angular, 

 and ribbed, like the shoulder-blade, or scapula. When they are to serve 

 as columns of support, they are cylindrical ; and as there is always 

 the utmost economy used by the Creator where it is needed, they are 

 made hollow, for it was known, as long ago as the first mammal was 

 made, that there was no loss of strength as a support in being so con- 



