LEUCOCYTE EXTRACT 289 



ing number of days. This period of rise represents the positive phase. 

 The second inoculation with vaccine should, according to Wright, be 

 made when the opsonic power is again beginning to sink after the highest 

 point of the positive phase. 



The facts of Wright's investigations have been given in the preceding 

 pages, purposely without critical considerations. The existence of 

 opsonic or phagocytosis stimulating substances in blood serum may be 

 accepted as fact. It is also of unquestionable value to the science of 

 immunity that renewed vigor has been infused into the investiga- 

 tion of active therapeutic immunization. The far-reaching claims of 

 therapeutic benefit, which have been made by Wright and his school, 

 however, have not yet received sufficient support by chnical observa- 

 tion to be fully accepted, although intelligent application of this treat- 

 ment in suitable cases has undoubtedly proved its therapeutic value. 



LEUCOCYTE EXTRACT 



In the foregoing sections upon Phagocytosis and Opsonins, we have 

 discussed the protective action exerted by the living leucocytes against 

 bacterial infection and the relation of these cells to the blood serum. 

 We have seen, furthermore, that, while our knowledge of the blood 

 serum, as developed at present, shows that phagocytes may be aided 

 by this in the ingestion of bacteria, the subsequent digestion of the 

 germs, and possibly the neutralization or destruction of their intracel- 

 lular poisons, is, as far as we know, largely accomplished by the unaided 

 phagocytic cell. It is an obvious thought, therefore, that, in the struggle 

 with bacterial invaders, the leucocytic defenders might be considerably 

 re-enforced if they were furnished, as directly as possible, with a further 

 supply of the very weapons which they were using in the fight with 

 the microorganisms. With this thought as a point of departure. Hiss ' 

 conceived the plan of injecting into infected subjects the substances 

 composing the chief cells or all the cells usually found in exudates, in 

 the most diffusible form and as little changed by manipulation as possi- 

 ble; and he also assumed that extracts would be more efficacious than 

 living leucocytes themselves, since if diffusible they would be distrib- 

 uted impartially to all parts of the body by the circulatory mechan- 

 ism. They would then, as quickly as absorption would permit, relieve 

 the fatigued leucocyte and also protect by any toxin-neutralizing or 

 otherpower they might possess, 'the cells of highly specialized functions. 



' Hiss, Jour. Med. Res., N. S., xiv, 3, 1908. 



