i62 Disturbances of the Blood. 



regarded as entirely destroyed or as seriously impaired in its 

 vitality.] It is readily observed in suppurations undergoing 

 metastasis (cf. metastasis), in swine erysipelas and other bac- 

 terisemias, that many of the leucocytes are loaded with the specific 

 germs. 



Negative chemotaxis, too, the movement of the leucocytes away 

 from certain poisons or more frequently the mere failure of attrac- 

 tion of the cell toward these substances, is capable of explaining a 

 number of points connected with disease and immunity. For ex- 

 ample, as shown by the extremely interesting studies of Besson, 

 Leclainche-Vallee, Vaillard and A^incent, non-virulent but living 

 germs (spores) of tetanus, malignant oedema and blackleg are 

 englobed by leucocytes and ingested and thus prevented from de- 

 velopment and from becoming virulent ; virulent germs of these 

 same sorts, however, prevent the leucocytes from entering the tis- 

 sues because of the toxines to which they give origin and are 

 therefore not taken up by the phagocytes, but continue their harm- 

 ful action upon the tissues in which they exist. 



The general group of leucocytes in the blood is subject to con- 

 siderable variation in number, even under normal conditions. 

 After taking food or violent muscular exercise there may be 

 uniformly observed an increase in their number ( physiological 

 leucocytosis or hypcrlcucocytosis) , apparently occasioned by the 

 attractive influence exerted by various proteid matters, fatigue 

 stuffs, etc., which have entered the blood. In inflammations, sup- 

 purations, and infectious fevers a similar increase in the number 

 of V leucocytes distributed throughout the blood occurs {pathological 

 hyperleucocytosis) , similarly ascribable, so far as indicated by ex- 

 periment, to chemical attraction and the circulation in the blood 

 of substances stimulating the leucocyte-forming tissues to greater 

 production. (Injection of bacterial proteins and other proteids into 

 the blood is particularly likely to be followed by hyperleucocytosis). 

 [While there are a few exceptions to the usual occurrence of 

 leucocytosis in acute infections, it is in a general way to be in- 

 terpreted as an unfavorable feature when such increase fails to 

 take place (leucopenia) ; either the subject being in such deterio- 

 rated state that the usual reaction is impossible and the resistance 

 to the disease much below par, or the smallness of number of these 

 protective cells itself determining the failure of sufficient antago- 

 nism. Cases marked by such unusual leucopenia, with the excep- 

 tion as above suggested of a few special forms of disease, are apt 

 to terminate fatally. 



