RELATION OF LEUKOCYTES TO IMMUNITY 309 



aleuronat emulsions were made in rabbits and, after about 24 hours, 

 the resulting exudates were taken away with sterile pipettes and 

 centrifugalized before clotting could take place; the serum was de- 

 canted and the leucocytes then emulsified in distilled water, in quan- 

 tity about equal to the amount of serum poured off. In this the leu-v 

 cocytes were allowed to stand for a few hours at incubator tempera- 

 ture, and then in the ice-box until used. For his experimental w r ork 

 in both animals and man, in most instances, not only the clear super- 

 natant fluid was injected, but the cell residue as well. 



With leucocytic extracts so prepared Hiss treated staphylococ- 

 cus, typhoid bacillus, pneumococcus, streptococcus, and meningococ- 

 cus infections in rabbits and obtained results which justified him in 

 concluding that the leucocyte extract exerted strong protective action 

 in all of these cases. Many of his animals survived infections fatal 

 to controls even when the treatment was delayed as long as 24 hours 

 after infection. Subsequently Hiss and Zinsser 53 treated series of 

 patients, ill with pneumonia, meningitis, and staphylococcus infec- 

 tions, with leucocyte extracts prepared by the method of Hiss, and 

 felt that they were justified in concluding that in many cases, at 

 least, the course of the disease was favorably influenced by the leuco- 

 cyte extract. Favorable results have since then been obtained also by 

 Lambert in erysipelas, and by Hiss and Dwyer in a variety of con- 

 ditions. 



While there seems to be little question about the actually favor- 

 able influence of the leucocyte extract, both in experiments with 

 animals and in the treatment of human cases, there has been consid- 

 erable difficulty in determining the reasons for this influence. In 

 subsequent studies Hiss and Zinsser (loc. cit.) were able to show that 

 the extracts did not favor phagocytosis and that the moderate bacteri- 

 cidal properties possessed by the leucocytic substances could not ac- 

 count for their effectiveness. There did seem to be a more rapid 

 accumulation of phagocytes in the peritoneal cavities of guinea pigs 

 infected with cholera spirilla when leucocyte extract was injected 

 with the bacteria, and it is not impossible, in fact, it seems probable 

 to the writer, from subsequent experience, that the protective prop- 

 erties of the leucocyte extracts are attributable, in part at least, to 

 their positively chemotactic effect. 



We are inclined to believe at present that the beneficial effects of leucocyte 

 extracts are based on the same principles as those which determine the reactions 

 following on the injection of bacterial and any other protein. 



In this connection a very interesting problem has arisen namely, that spoken 

 of as the phenomenon of Specific Hyperleucocytosis. Bordet, as early as 1896, 

 made the following statement, ' ' Active immunity has also other characteristics, in 

 that there is an increase of the number of leucocytes, that is, an 'exaltation' of 

 the chemotactic sensibilities of the leucocytes." He suggests herein that an im- 

 munized animal may respond with a more powerful leucocytic reaction to the in- 

 jection of the infectious agent than would a normal animal similarly treated. This 



53 Hiss and Zinsser. Jour, of Med. Res., new series, Vol. 14, 1908. 



