LEUCOCYTE EXTRACT 289 



and upon the size of the dose given. It is usually completed within 

 twenty-four hours. After this, there is a gradual rise in the opsonic 

 power, at first rapid, later more slow, until a maximum is reached after a 

 varying 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 pre- 

 ceding without much critical consideration. Those features which con- 

 cern themselves with the proof of the opsonic properties of normal 

 and immune serum have been of the greatest scientific importance and 

 a great deal of benefit has accrued from the renewed attention turned 

 by him toward methods of active immunization in human beings. 

 Vaccine therapy in many conditions has- come to stay, although some 

 of the very extravagant earlier claims have had to fall down. It 

 is also pretty certain at present that the opsonic index measure- 

 ments as a guide to treatment is of very little value and may even mis- 

 lead. 



Leucocyte Extract. In the sections upon Phagocytosis and Op- 

 sonins, we have discussed the protective action exerted by the living 

 leucocytes against bacterial infection and the relation of these cells to 

 the blood serum; 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, arid 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 01 

 other power they might possess, the cells of highly specialized functions. 



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



