490 PATHOGENIC MICROORGANISMS 



pigs, less markedly for rabbits, and still less so for dogs. It is 

 slightly pathogenic for cattle, a question spoken of more extensively 

 below. 



Chemical Analysis of Tubercle Bacilli.' — Diligent efforts by many 

 investigators to isolate the specific toxins which lend tubercle bacilli 

 their pathogenic properties have led to careful chemical analysis of the 

 organisms. About 85.9 per cent of the bacillus consists of water; 20 

 to 26 per cent of the residue can be extracted with ether and alcohol. 

 This material consists of fatty. acids and waxy substances (fatty acids 

 in combination with the higher alcohols). The residue after alcohol- 

 ether extraction is composed chiefly of proteids. These can be extracted 

 with dilute alkaline solutions, and consist chiefly of nucleo-albumins. 

 A nuclein present in this fraction shows extremely high toxicity and 

 has,^ therefore, been suspected of being the pathogenic principle of the 

 bacillus. After these extractions the remainder contains "cellulose," 

 supposed to represent the framework of the cell membrane, and an ash 

 rich in calcium and magnesium. 



Toxins of the Tubercle Bacillus. — The Tuberculins. — Filtrates of 

 bouillon cultures of Bacillus tuberculosis ' will occasionally produce 

 shght emaciation when injected into guinea-pigs, and when administered 

 to tuberculous subjects in sufiicient quantity will give rise to marked 

 increase of temperature. It is likely, therefore, that the tubercle 

 bacillus actually secretes a soluble toxin.^ 



The chief toxic principles, however, of Bacillus tuberculosis are 

 probably endotoxins or bacterial proteins, bound during cell life to the 

 body of the bacillus. Dead bacilli will produce sterile abscesses when 

 injected into animals. Prudden and Ilodenpyl,^ Straus and Gamaleia,' 

 and others,' moreover, have shown that the injection of dead and care- 

 fully washed cultures of this bacillus will produce lesions histologi- 

 cally similar to those occurring after infection with the living germs, 

 and will often lead to marasmus and other systemic symptoms of 

 poisoning. 



The hope of actively immunizing with substances obtained from 



^ Hammerschlag, Cent. f. kHn. Med., 1891; Weyl, Deut. mad. Woch., 1891; De 

 Schweinitz and Dorset, Jour. Amer. Chem. Soc, 1895; Hammerschlag, loc. cit. 

 2 Behring, Berl. klin. Woch., 1899. 

 ^ Straus and Gamaleia, Arch. med. exp., 1891. 

 ' Denys, "Le Bouillon Filtr^," Louvain, 1905. 



* Prudden and Hodenpyl, N. Y. Med. Jour., June, 1891; Prudden, ibid., Dec. 5. 

 ^ Straus and Gamaleia, loc. cit. 

 ' Mafucd, Cent. f. allg. Path., 1890, 



