THEIR CAUSES, XATURE, AND PREVENTION. 179 



the sheep can withstand the effects of ahnost any degree of 

 cold it is most injuriously affected by cold and wet coiribined ; 

 and this is especially true of lambs. 



The perspiratory function of the skin is not the only function 

 of impoi-tance that it performs. It is a breathing or respiratory 

 organ also, though its powers in this direction are limited ; 

 nevertheless, if the skin is covered with some impermeable 

 material, such as varnish, or, as is frequently done in the case of 

 afhliation of lambs, with a lamb skin, the animal dies. It was 

 at one time thought that death in these cases was due to suffo- 

 cation ; now, however, it is believed to be due to poisoning, as 

 the temperature lowers materially, such a proceeding would cer- 

 tainly arrest the excretory function of the skin most effectually. 



That oxygen is taken in and carbonic acid given off by the 

 skin has been sho\vn by direct experiment. 



The excretory function of the skin is of the highest import- 

 ance. The sweat usually contains common salt, ammonia and 

 fatty acids in var\ang though small proportions ; but it is fur- 

 ther known that under some conditions other materials are 

 excreted, such as waste products and even colouring matter, 

 and in some instances certain constituents of the blood also. 

 In disease of the kidnej's matters usually passed off by these 

 organs have been found in the sweat. 



In all animals a certain quantity of fatty (sebaceous) matter, 

 known as yolk in the sheep, is secreted by the skin, but in no 

 animal is the amount so great as in the sheep, and it is early 

 noticed that in an unhealthy animal the fleece becomes diy and 

 harsh instead of greasy. 



Arrest of this secretion is of most importance in the case of 

 animals exposed to cold and wet, for it leaves the skin at the 

 mercy of these influences and allows of the ready absorption 

 of the latter. Yolk contains a large percentage of potash 

 which is obtained from the soil and removed in the wool. 



Having considered the influence of the action of the different 

 organs of the body in the production of disease, or rather I 

 should say in the preservation of health, I will next look at the 

 influence of foods and for brevity's sake will group these foods 

 — 1st, into those of a succulent character, i.e., containing large 

 proportions of water ; 2nd, into those rich in heat-producing 

 material ; and 3rd, into those rich in flesh-forming substances. 



(1) Succulent Foods. — It follows, as certain as light follows 

 darkness, that in proportion as Avatery elements increase 

 nutritive elements decrease, and in no class of food is this so 

 strikingly shown as in turnips which contain about 90 parts of 

 water to 10 of nutritive matter. The same applies to grass 

 which has been rushed by excess of moisture, artificial stimuli 

 and warmth. 



