VETERINARY PATHOLOGY. 



produces ferments that digest food substances, as well as necro- 

 tic tissue as inflammatory exudate. The phagocytic action of 

 leucocytes is largely dependent upon the fact that the substances 

 phagocytized have been previouslv rendered inert. Connective 

 tissue cells are closely related to leucocytes in their power of 

 producing digestive ferments. Endothelial cells produce fer- 

 ments which aided by the leucocytic ferment, dissolve and devour 

 thrombi and emboli. On the other hand nerve cells are quite 

 selective in their food requirements and they have practically 

 no pow er of prciducing digestive ferments. 



The foods required by cells are nitrogenous and non-nitro- 

 genous. Nitrogenous nutrients are used in the construction and 

 maintainance of the cell protoplasm. The non-nitrogenous foods 

 are essentiallv carbohydrates and fats which are consumed 

 when cnergv, in the form of either heat or motion, is liberated. 

 When non-nitrogenous foods are consumed in excess, some of 

 them ma-,- l)e stored as glycogen in the liver, or as fat in the 

 various part'^ of the l)ody, thus producing glycogenic or fatty in- 

 filtration. The consumption of nitrogenfius food in excess may 

 result in overwork of nitrogenous excretorv organs as in induced 

 albuminuria. Insufiicient supplv of carl^onaceous food produces 

 disturlicd metabolism, because of the necessarv conversion of 

 nitrogenous food or nitrogenous cell constituents into carl:)on- 

 aceous suljstances, in order that the body energy may be main- 

 tained. Diminished supply of nitrogenous foods is temporarily 

 compensated for by consumption of the protoplasm of the l)ody 

 cells, if tlie nitrogenous food supply is materially diminished 

 fiir a liing time (jr entirely withheld, the bodv cells atroph_v, 

 degenerate, and ultimately die. 



The waste jiroducts are also divisible into two classes, nitro- 

 genous and non-nitrogenous. The nitrogenous waste substances 

 arc urea, or some allied ])roduct. The\- represent kataliolic pro- 

 ducts, i. e., the results of destructive changes in the cell proto- 

 pl.'isni. The car1ioh}-drates and fats are almost entireh- converted 

 into cnerc;y ; caribou dioxide and water l)eing the chief katal:iolic 

 prriducts. 



Irritability. — Irritability is tlie property of certain cells which 

 enables them to respond to stimuli. Stimuli may l)e chcmic, 

 thermic, electric or mechanic. The property of irritability is 

 vested especially in nerve cells, although other cells are slightly 

 irritaljic, e. ,t^-., muscle cells. The degree of sensitiveness varies 

 greatly in dift'ercnt species of animals and to a less extent in dif- 

 ferent individuals of the same species. Thus tlie thoroughbred 

 horse has a more sensitive skin than the draft horse. Irrital)ility 



