24 THE HORSE IN MOTION. 



structed. It was long afterwards discovered by man, and the law was 

 learned by him, that the lateral strengths of two cylindrical bones of 

 equal weight and length, one being solid and the other hollow, are to 

 each other as their diameters ; and the spaces in the shafts of these 

 bones, being needless for the purpose of support, are made depositories 

 of fat or marrow for fuel, literally, coal-bunkers, as are all the angu- 

 lar spaces not needed for more important uses throughout the body, 

 by means of which heat is developed, which primarily is the source of 

 all motion in the animate as well as the inanimate world. 



The extremities of these bony columns are spread out to give 

 broader articulating surfaces ; at the same time the single hollow of 

 the shaft is divided into innumerable small ones, so that greater 

 strength is attained to resist the wrenching force to which they are 

 liable, without increase of weight ; roughened ridges, spines, and pro- 

 tuberances * are formed to give greater surface for the attachment of 

 muscles. For the purpose of still further increasing the surface for 

 attachment of muscles, supplemental bones are added, as in the splint 

 bones, or, as they are called by anatomists, the little metacarpels, 

 which not only serve to widen the articulating surface, but, by a strong 

 ligamentous membrane that connects them with the main pillar, give 

 the necessary space for attachment of important muscles, and where 

 the distance from the centre of motion renders the reduction of weight 

 very important, as the rapidity with which these extremities move 

 increases greatly with the distance from the centre of motion. The 

 bones are composed of animal and earthy matter, in the proportion 

 of about one of the former to two of the latter. If the proportion 

 of the former is increased, they will bend under the force applied to 



* Atheists maintain that function makes the organ ; but how can we conceive of function 

 without previous conception of the organ ? What conception can be formed of sight without 

 the existence of the eye ? It is held by them that the roughened ridges and protuberances of 

 bone are developed by traction of muscles upon the bony surfaces. If this is so, why is it that 

 the surface of the bone above the acetabulum which receives the insertion of the recttts fctno- 

 ris is smooth ? It certainly is not because there is want of traction on the part of that muscle. 

 On the other hand, the tensor vaince femoris and the superficial glutens, whose insertions are 

 low down on the femur for the necessary leverage, must find room between other muscles, and 

 a rough protuberance is formed to give the most surface for attachment in the least space. 



