SHEEP diseases: causes, nature and prevention. 
263 
That oxygen is taken in and carbonic acid given off by the 
skin has been shown by direct experiment. 
The excretory function of the shin is of the highest importance. 
The sweat usually contains common salt, ammonia and fatty acids 
in varying though small proportions; but it is further known that 
under some conditions other materials are excreted, such as waste 
products and even coloring matter, and in some instances certain 
constituents of the blood also. In disease of the kidneys 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 dry 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 watery elements increase nutritive 
elements decrease, and in no class of food is this so strikingly 
shown as in turnips, which contain about ninety parts of water to 
ten of nutritive matter. The same applies to grass which has 
been rushed by excess of moisture, artificial stimuli and warmth. 
Now, if these foods are not supplemented by others of a nutri¬ 
tive character disastrous results must and do follow; the class of 
diseases produced being those in which lowered vitality and debility 
with dropsies—such as water braxv, shell sickness, vanquish or 
trembles—are marked. The lowering influences of such foods 
