8 BOARD OF AGRICULTURE. 



latoiy appendages of vertebrate animals. In the fm of the 

 fish, which is analagous to the human arm, there is a multi- 

 plicity of rays, but higher in the series the number is reduced 

 to five phalangial rows, of which the monodactyle foot of the 

 horse is the lowest expression, and answers to the middle 

 finger of the human hand. 



The law by which these toes are lost is interesting to us, 

 as well marked examples of such modifications are found in 

 the domestic animals. The first to disappear is the thumb, 

 then we have a four-toed foot like the hog and the deer. 

 Next, the fifth row, or little finger is lost, and this leaves the 

 tridactyle foot, which we have already considered. 



Having thus briefly pointed out a few facts concerning the 

 natural history of the horse, let us now turn our attention to 

 another department of our subject, which, I trust, will be far 

 more interesting to those who have the guardianship of this 

 noble animal. But as it is not bur mission on this occasion 

 to treat of the general maladies of the equine system we will 

 limit our inquiries to the pathological, or diseased conditions 

 of the bones, and of some of the adjacent tissues. 



Comparative anatomists have clearly shown that the entire 

 series of vertebrate animals, including man, are built upon 

 the same general plan of structure. The chemist has assured 

 us that the bones of all animals are composed of the same 

 proximate principles, or ingredients, though the relative quan- 

 tities of these several principles vary considerably in the dif- 

 ferent types, orders, and species. And the physiologist has 

 conclusively proved by his microscopic examinations that the 

 blood of fishes, reptiles, birds, and mammals, contains the 

 sanle anatomical granules and cells as is found in the blood 

 of man. Now, in view of all these facts, why may we not 

 suppose that the domestic animals are afflicted with the same 

 diseases as we are, differing only in degree ? 



Upon this basis we shall inquire into the pathological oste- 

 ology of the horse, though we do not expect to find all those 

 loathsome diseases of the bones in the equine system which 

 so frequently visit the frail body of mortal man. 



The diseases of the bones maybe divided into three classes. 

 First, we will consider those diseased conditions which affect 



