lo Dec, 1908.] Diseases of the Blood. 751 



by heightened colour of the visible mucous membranes, but not necessarilv 

 increased vigour either of the circulation or the body generally. The pulse 

 is usually full and strong and there is a tendency to lay on fat. Plethora 

 is only untoward when it is carried to excess in which case the tendency 

 to internal congestions and haemorrhages (apoplexy) and to acute inflam- 

 matory affections is great. 



Treatment should aim at a diminution of the amount of nutritive 

 material carried into the blood. This may be brought about by limiting 

 the diet or by giving the laxative medicine. Active treatment of con- 

 gestion resulting from plethora would include blood letting (see page 6t, 

 Vol. V.) & \ K 6 . 



Leucaemia. 



This condition, also called leucocythsemia, is " characterized by a con- 

 siderable increase in the number of white corpuscles in the blood, by 

 diminution in that of the red corpuscles, and by changes in the spleen, 

 lymphatic glands, bone-marrow and other organs." {Green). It has 

 been but rarely observed in the lower animals. By " leucocyte sis " is 

 meant an increase of the number of white corpuscles only without any 

 other change. 



Hyperaemia or Congestion. 



Hyperemia or Congestion is an excess of blood in the more or less 

 dilated vessels of a part, and according as it is the arteries or the veins 

 that are engorged the terms active congestion (arterial hypersemia) and 

 passive congestion (venous hypersemia) are applied. In active congestion 

 the engorgement of the vessel with blood is always accompanied bv an 

 acceleration of flow, while in venous congestion the flow is retarded. Con- 

 gestion is the premonitory stage of inflammation. 



Various organs of the body, particularly the lungs and liver, are liable 

 to congestion, constituting definite disease of the organs which will be 

 dealt with along with the other diseases of such organs. 



Apop'exy. 



Apoplexy in a general sense consists in a rupture of the wall of a 

 blood vessel Avith exudation of blood. It frequently follows on an exag- 

 gerated condition of hyperaemia the vessels of the brain and lungs being 

 most liable. Apoplexy is not always the result of engorgement ; it mav be 

 brought about by a weakening or diseased condition of the wall of the 

 blood vessel. 



Inflammation. 



Inflammation is modemly described as " the reaction of the tissues 

 to irritation." It is primarily Kowever a process in which a change takes 

 place in the wall of the blood vessels of the inflamed part and in the 

 behaviour of the blood in such vessels. The various processes v/hich con- 

 stitute the phenomena of inflammation are always the result of irritation ; 

 and it is this fact that irritation is essential which constitutes the diff^erence 

 between inflammation and other pathological processes, e.g., tumour forma- 

 ton, atrophy, gangrene, degenerations, &c. 



