72 • AMERICAN FARMER'S HORSE BOOK 



THE CAUSES OF BIG HEAD. 



The fact just stated points strongly to the conclusion that 

 among the many causes which combine to produce big head, 

 is the water found in the sections where it prevails, which is 

 generally strongly impregnated with sulphur, iron, and other 

 minerals. It is soft, such as is found in freestone formations, 

 and entirely destitute of lime, a substance entering largely 

 into the composition of the bones. The bones are composed 

 mainly of phosphate of lime, a combination of lime and 

 phosphorus. For the former, the horse is chiefly dependent 

 upon the water which he drinks., his food supplying the latter. 

 Fresh water does not furnish phosphorus, nor vegetation 

 lime, except in very limited quantities. The lime contained 

 in some water is not free, but exists in combination with 

 other substances, and in such cases there will be an excess 

 of phosphorus in the secretions above what is needed to 

 supply materials for the growth and repair of the bones. 



Water performs the office of a solvent in the digestive 

 functions of the stomach. It softens the food into chyme, 

 which, passing into the small intestines, there receives the 

 gastric secretions of the hepatic and biliary ducts, and by 

 their aid is still further digested. The nutritive particles 

 are next extracted, and, in the form of chyle, are conveyed 

 to the blood. Lime is mechanically combined with water, 

 and, when it is free, unites readily in this process with the 

 chyle, and with it is carried by the blood to the bones. 

 Phosphorus is secreted from the food, and supplied to the 

 bones in the same manner. 



The water in Western • Tennessee, Northern Mississippi, 

 and Eastern Arkansas is not only singularly devoid of lime, 

 but is remarkable for containing so many other minerals. 

 This condition of the water, however, can not be regarded 

 as the sole cause of big head. In some parts of our coun- 

 try, where there is still less lime in the water, the disease 

 is well-ni^h unknown, and, even in the sections named, 

 many horses escape. But that it is, at least, a predisposing 

 agency can not reasonably be doubted. 



