288 INFECTION AND RESISTANCE 



direct study, since the conditions within the living body are subject 

 to a large number of modifying factors, and experiments upon the 

 isolated cells, in vitro, even under conditions of the most careful 

 technique, are fraught with much unavoidable injury to the cells. 

 However, enough has been learned to indicate that these cells are 

 subject to the phenomena of chemotaxis or tropism just as are inde- 

 pendent unicellular forms, and that they may be attracted or re- 

 pelled by a variety of organic and inorganic substances. Leber 31 

 was one of the first to study this in his work upon inflammation. 

 He found that leukocytes were actively attracted by powdered cop- 

 per and mercury compounds, but not by powdered gold or iron. He 

 also observed that dead bacteria exerted a similar positive chemo- 

 tactic influence, and Buchner 32 later succeeded in extracting sub- 

 stances from various bacteria which possessed similar properties. It 

 appears, from these and other investigations, that the power of stim- 

 ulating positive chemotaxis is a general property of bacterial pro- 

 teins, equally evident in bacterial extracts, dead bacteria, or the liv- 

 ing organisms. It is likely, therefore, that the attraction of leu- 

 kocytes toward the point of bacterial invasion is, in part at least, 

 due to the properties of the bacterial proteins themselves. That this, 

 however, is not the whole story is evident from the work of Massart 

 and Bordet, 33 who showed that the products of cell destruction and 

 disintegration possess similar positively chemotactic properties. This 

 is true not only of the products of disintegrated tissue cells, but of 

 those of the destroyed leukocytes themselves. Thus it appears that 

 when any injury of tissue takes place, a stimulus which attracts 

 leukocytes results, even when the injury is not accompanied by bac- 

 terial invasion. This would explain the participation of leukocytes 

 in reactions to injury, and in inflammations not of bacterial origin, 

 and their local accumulation following the injection of insoluble 

 inorganic substances. 



When bacteria are actually present, however, the added stimulus 

 due to the diffusion of bacterial proteins probably increases the 

 process to a degree often sufficient to meet the added requirements 

 for protection. Following this, both the destruction of tissues, of 

 bacteria, and of leukocytes may together exert a cumulative chemo- 

 tactic power which continues the process proportionately with the 

 extent of the lesion. 



It is of the utmost importance, therefore, to ascertain whether 

 or not any substances derived from bacteria may, under any circum- 

 stances, exert a repellent or negatively chemotactic power. If we 

 infect an animal intraperitoneally with virulent bacteria, in doses 



31 Leber. FortscJir. der Med., 1888; also "Die Entstehung der Ent- 

 ziindung," Engelmann, Leipzig, 1891. 



32 Buchner. Berl. klin. Woch., Vol. 27, No. 30, 1890. 



33 Massart and Bordet. Ann. de I'Inst. Past., Vol. 5, 1891. 



