122 ROLE OF THE LEUCOCYTES 



the toxin will ultimately reach the tissues. And it is probable 

 that the beneficial effect of early as compared with late injections 

 of diphtheria toxin may be dependent in part on the fact that in 

 this disease the leucocytes are very apt to suffer degenerative 

 changes which doubtless impair their defensive powers. Ewing 

 believes that the variations in the staining capacity of these cells 

 (loss of chromatin being an early and easily recognized sign of 

 their degeneration) might be utilized as a means of prognosis, and 

 points out that in cases which recover the staining quality of many 

 of the leucocytes undergoes a rapid improvement after the injec- 

 tion of antitoxin, whereas in fatal cases this change could not be 

 detected. As a rule the total number of leucocytes is diminished 

 immediately after the injection of antitoxin, but in some fatal 

 cases the previously existing leucocytosis may remain or even 

 increase. This fall in the total number of leucocytes is probably 

 to be accounted for by the neutralization of the toxin, so that 

 fresh white corpuscles are no longer attracted from the bone- 

 marrow by positive chemotaxis, whilst the old and injured cells 

 remain in the spleen or other internal organs, no longer circulating 

 in the blood. In cases which die the reduction in the number of 

 leucocytes may be followed by a subsequent rise. 



Here also we must refer to numerous researches, emanating 

 more especially from the French school, which go to show that 

 substances which are certainly devoid of true specific antagonism 

 have nevertheless the power of preventing or diminishing the 

 action of toxins in virtue of causing an increased inflow of leuco- 

 cytes to the region into which the injections are made. This 

 question has been more especially investigated in regard to the 

 effect of this artificially produced local leucocytosis in causing 

 local bacterial immunity, but Calmette and Delecarde have shown 

 that the peritoneal injections of ordinary broth cause a certain 

 degree of immunity to abrin, whereas normal saline solution has 

 no such power. The former substance is a powerful agent in 

 attracting leucocytes, whilst the latter is much less potent in this 

 respect, though by no means devoid of activity. Substances which 

 have the power of increasing the action of the leucocytes in this 

 way are sometimes termed "stimulins," but the word should be 

 avoided. The action of leucocytes in any region may be in- 

 creased by many methods, the chief of which are : (i) attracting 

 larger numbers by means of substances having a positive chemo- 

 tactic action ; (2) stimulating the activity of the leucocytes ; and 



