17 i SHEEP DISEASES: 



pale colour (pallor) of the visible mucous membranes, — as of the 

 eye, nose and mouth ; and in man, in the blanching of the skin. 

 In all animals the effects of its loss are seen in the excessive 

 rapidity of respiration for the purpose of compensating, by the 

 quantity taken into the lungs, for the small quantity of oxygen 

 which the blood cells are capable of carrying to the tissues. 



It is now demonstrated also that iron acts as a stimulant to 

 the liver. 



An animal in whose body iron is deficient becomes compara- 

 tively bloodless though its carcase may be laden with fat; it is said 

 to be ancemic, and if this condition is pushed too far it dies. 



Iron may exist in abundance, but by the influence of adverse 

 agencies, such as the action of disease or disease germs, the red 

 cells may be incapable of appropriating it ; and thus, in the 

 midst of plenty an animal may die • of oxygen starvation. If 

 iron is assimilated in superabundance an opposite extreme is 

 induced, viz., excess of hlood (hyperaemia), and inflammations 

 may result. 



Not only phosphorus, but, as has recently been shown, a 

 salt of potash (the chlorate) has the power of so changing the 

 colourinsf matter of the blood as to render it useless and to cause 

 it to be passed out by the kidneys, giving to the urine a peculiar 

 but characteristic colour. Carbonic acid renders the blood dark 

 and displaces oxygen. Carbonic oxide heightens the colour 

 but brings about such a change in the condition of the iron as 

 effectually to j)revent re-oxidation ; hence the primary and 

 secondary effects of exposure to the gases given off in combus- 

 tion or fires and hence the blood-stained urine we sometimes 

 see passed by animals which have been exposed to the influence 

 of those gases in burning stables and cowsheds. 



Having described some of the characters of the blood, I will now 

 consider the influence exerted upon it by the more important 

 organs and functions of the body, viz., by digestion and assimila- 

 tion, by oxidation and nutrition ; by the liver, the bowels, the 

 mesenteric glands, the kidneys, the spleen, the lungs and the skin. 



Digestion. — The first act of digestion is performed in the 

 mouth when food is broken up by the teeth and exposed to the 

 action of the saliva which secretion converts the starchy matter 

 it contains into sugar by the action of a ferment (ptyalin). The 

 process is most perfect in ruminants. The second act in diges- 

 tion takes place in the stomach, where the acid secretion — gastric 

 juice (succus gastricus) — dissolves mineral and other matters, 

 while by the action of a second ferment (pepsin) albumen is 

 rendered more soluble and converted into substances known as 

 peptones. The third act in digestion is performed in the small 

 bowels where the food meets with the secretion of the pancreas 

 (sweetbread), the pancreatic juice ; and with the secretion of the 



