[ 6,, ] 



the red colour of the corpuscles is due. An adequate supply 

 of iron with the food is therefore necessary to keep the 

 blood in health. Where there is deficiency of iron in the 

 food the blood becomes veinous or dark in character and 

 loses the bright arterial scarlet appearance. 



1.038. Many physiologists recognise the existence in the 

 blood of a third corpuscle which they call the haematoblast 

 or blood-former. The hapmatoblast is supposed to give rise 

 to leucocytes and the leucocytes to the red corpuscles. 



1.039. The serum or fluid portion of the blood contains two 

 substances called respectively fibrinogen and fibrinoplastin. 

 When blood is let out it co-agulates, the co-agulation being 

 due to a ferment acting on fibrinogen and fibrinoplastin, 

 which convert them from a fluid to a solid state. 



1.040. An excess of water in the food results, onjthe other 

 hand, * in the colouring matter of the red corpuscles being 

 partly washed out and the white corpuscles also getting 

 macerated. The turgidity of the capillaries resulting from 

 excessive absorption of water, leads to their walls getting 

 weakened and their vitality lowered. Serum escapes from the 

 capillaries, which are so weakened, into the tissues and cavities 

 of the body. Ancemia and dropsy may follow a protracted 

 course of feeding with an excess of succulent food. Reple- 

 tion and congestion of important organs are frequently 

 caused by an excessive draught of water, specially when 

 the system is in too heated a condition. Giving of water 

 to horses and other animals after work when by perspiration 

 the blood has become thick, is the right plan, but when the 

 heating of the system is excessive and circulation very 

 rapid, a draught of water often results in congestion of 

 lungs or of some other organ. A middle course, therefore, 

 is advisable, L ., in too heated a condition an animal must 

 be allowed to cool down a little by gentle walking or by 

 wisping, before water is given to it ; but if the work has 

 not been of a violent but of a light character, giving of water 



