IMMUNITY AGAINST MICROBES. 439 



justijfiable to argue from this fact that the inflammatory liquids 

 present in the membrane possess a microbe-killing power, but, 

 judging from the number of dead leucocytes present in the 

 membrane, it is far more probable that these partially digested 

 microbes were originally contained in a leucocyte which had 

 died and undergone liquefaction. 



Similar, but far more interesting, facts are noticed when 

 we examine the processes taking place in chronic infectious 

 diseases, such as tubercle and actinomycosis. Shortly stated, 

 a nodule of tubercle or actinomycosis contains, besides the 

 specific parasites, three kinds of amoeboid cells :^ 1st, small uni- 

 or multi-nucleated cells ; 2nd, large mononucleated or epi- 

 thelioid cells ; and 3rd, multinucleated giant-cells. 



The development of giant-cells has been well studied in the 

 Spermophilus guttatus by Metschnikoff.^ When a Sper- 

 raophilus guttatus is inoculated with a pure culture of the 

 tubercle bacillus no tuberculous formations are found in any 

 of its organs after death, but microscopical examination of the 

 liver, spleen, and lymphatic glands shows these organs to be 

 crammed with giant-cells, the development of which can be 

 followed with ease. 



These cells are derived from isolated epithelioid cells in 

 the following manner : — The nucleus of an epithelioid cell 

 assumes a star-shaped appearance, and each of the rays so 

 produced is ultimately converted into one of the nuclei of the 

 giant-cells. A swelling then forms at the extremity of each 

 ray, which at first appears to be homogeneous; but later on 

 becomes filled by a transparent mass with irregular outlines, 

 the mass resembling a new nucleus. The chromatin now 

 slowly divides into a peripheral and a central part, and in this 

 way one or more nuclei are formed which are connected by a 

 thread only with the remainder of the old star-shaped nucleus. 

 These masses, which in the first stage are extremely irregular 

 in form and outline, finally become detached and assume the 



• I intend to discuss Baumgarten's and Weigert's views in another part of 

 this paper. 



» Metschuikoff, ' Vircliow's Archiv,' vol. cxiii, 1888. 



