STABLE IMPURITIES. 45 



get a sufficiency of bone and substance for weight carrying 

 and heavy draught purposes. 



The accommodation of the system to new surroundings is 

 well illustrated by the readiness with which the skin responds 

 to the stimulus of cold, or to the sedative action of heat, in 

 the growth of the epidermis. A striking instance of this 

 fact is afforded by the change in the order of shedding the 

 coat which takes place among Australian horses that are 

 imported into India. These animals, which, in the Antipodes, 

 get their winter coat in the spring, and their summer one 

 in the autumn, at first suffer during the Indian hot months 

 from wearing a coat which is abnormally heavy for the 

 climate of their new place of residence. However, in a 

 comparatively short time, say, in a couple of years, the 

 order of shedding the coat changes to that of Indian horses, 

 with an improved state of health. 



STABLE IMPURITIES. 



I am indebted chiefly to Dr. W. H. Willcox, B.Sc., A.I.C., for 

 the details connected with chemistry in this section, which 

 has been written for readers who are acquainted with that 

 science. 



Stable impurities may be classed as follows : 



1. Exhalations which are given off from the lungs and skin, 

 and which consist chiefly of carbonic acid and water. 



2. Urine, dung, and the products formed by their decom- 

 position. 



3. Bacteria (germs of decomposition and disease), which 

 are adventitious bodies. 



The decomposition of urine may be explained as fol- 

 lows : 



According to Is. Pierre the urine of the horse is composed, 

 on an average, of 90.5 per cent, of water, 4 per cent, of 

 mineral matter, and 5.5 per cent, of organic matter, which 



