250 INFLAMMATION 



the same animals are positively heliotropic and swarm to the surface illuminated 

 brightly by a lantern. Variations in heliotropism may, in some cases, be explained 

 as due to chemical changes that occur in the organism, which explanation is made 

 more probable by J. Loeb's experiments, which show that change in composition 

 in the fluid in which animals are suspended may cause a complete reversal in their 

 reaction to a constant stimulus. Motile bacteria seem to behave much like cili- 

 ated protozoa in their reaction to stimuli. 



Chemotaxis of Leucocytes^ 



That leucocytes come to the site of an infection because of chemical 

 substances produced by bacteria at this point, that is to say, through 

 chemotaxis, was first clearly pointed out by Leber^° in 1879, who 

 likened the attraction of such substances for leucocytes to the effect 

 of malic acid upon spermatozoids as shown by Pfeffer. He found 

 that in keratitis, leucocytes invaded the avascular cornea from the dis- 

 tant vessels, not in an irregular manner, but all moved directly toward 

 the point of infection, where they collected. As dead cultures of 

 staphylococci produced a similar, although less marked, accumulation 

 of leucocytes, he sought the chemotactic substance in their bodies, and 

 isolated a crystalline, heat-resisting substance, phlogosin, which at- 

 tracted leucocytes in animal tissues. He also observed that capillary 

 tubes filled with phlogosin or with staphylococci were soon invaded 

 by masses of leucocytes. 



Since Leber's experiments, many other investigations have been 

 made showing that chemical substances of many different origins other 

 than bacterial exert a chemotactic influence on leucocytes. Some sub- 

 stances are indifferent in effect, most are positive, while some are be- 

 lieved to repel leucocytes; i. e., are negatively chemotactic. 



Negative Chemotaxis. — Probably the substances that repel leuco- 

 cytes are few in number; Kanthack, indeed, doubted the existence of 

 really negative chemotactic action upon leucocytes. Verigo" also 

 considers that as yet no actual negative chemotaxis has been satisfac- 

 torily demonstrated; but, by analogy with the effects of chemicals on 

 amebae, ciliata, and plasmodial forms, which all show a decided nega- 

 tive chemotaxis under certain influences, it would seem most prob- 

 able that leucocytes also should be repelled as well as attracted by 

 chemicals.'^ 



N on -bacterial Chemotactic Substances. — One of the earliest 

 significant studies of the effects of non-bacterial substances upon chem- 

 otaxis was made by Massart and Bordet,'^ who showed that products 



" Review of literature on leucocytes by llelly, Ergeb. allg. Pathol., 1914(17(n), 1. 



'0 Fortschritte der Med., 1888 (6), 460. 



" Arch. d. M('d. oxper., 1901 (13), 585. 



"* Salomonsen's observation (Festskrift vcd iiulviclscMi af Statrns Scrum Iii- 

 stitut, Kopenhagen, 1902, Art. XII), that ciliated infusoria wlu-ii killed show a 

 strong negative effect on other ciliates, is of much interest, particularly as it 

 seems to he tlu; ojjposite of the positively chemotactic effect of dead upon living 

 leucocytes. Tlu; negative reaction of different ciliata was specific for their own 

 kind quantitatively, but not qualitatively. 



'•^ Ann. d. I'lnst. Pasteur, 1891 (5), 417. 



