RELATION OF LEUKOCYTES TO IMMUNITY 309 



Hiss 52 worked at first with extracts of dog, rabbit, and guinea 

 pig leukocytes; later he confined himself entirely to rabbit leuko- 

 cytes. He extracted the leukocytes at first by repeated freezing and 

 thawing in physiological salt solution, but the technique of his sub- 

 sequent work was uniformly as follows: Intrapleural injections of 

 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 leukocytes then emulsified in distilled water, in quan- 

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

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

 ture, and then in the ice-box until used. For his experimental work' 

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

 natant fluid was injected, but the cell residue as well; since Hiss 

 realized that the extractions were necessarily incomplete. In in- 

 travenous work, of course, the supernatant fluid alone was injected. 



With leukocytic 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 leukocyte 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 leukocyte 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 leuko- 

 cyte extract. Favorable results have since then been obtained also 

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

 conditions. Dwyer has used the extract in various infections of the 

 eye, ear, nose, and throat. 



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

 able influence of the leukocyte 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 leukocytic 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 leukocyte 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- 



52 Hiss. Jour, of Med. Res., new series, Vol. 14, 1908. 



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



