TUBERCULINE. 169 



porcelain filter. The extract thus obtained, containing 40 per 

 cent, of glycerin, was very stable. 



After many fruitless attempts KOCH abandoned the idea of further 

 purification. His method has been frequently modified. NOCARD 1 first 

 heated the cultures to 110 C. before treating them in the same way ; he 

 contented himself with filtration through paper, since his preparations 

 were obviously already sterile. MABAGLiANO,' 2 and, subsequently, FRENKEL 

 and BRONSTEIN (loc. cit.), used a method of boiling, eventually in auto- 

 claves, in the preparation of products very similar to tuberculine. 



BE BRING 3 extracted from tuberculine a substance akin to 

 mucin by means of soda solution, and fatty substances by means 

 of ether, and in this way claimed to have obtained a preparation 

 about twenty times as poisonous as before. 



NiEMANN, 4 too, has endeavoured, though without any particular success, 

 to obtain strong tuberculine preparations by precipitation with alcohol. 



As regards the toxic value of these preparations the results 

 obtained by these investigators have been supplemented by 

 GRAMATSCHiKOFF, 5 who proved that tuberculine was a blood 

 poison, and by v. LINGELSHEIM, G who proposed to determine a 

 normal unit of toxic activity by means of intercerebral injections. 



CARRiERE 7 found that fairly considerable alterations in the 

 liver and kidneys followed the injection of tuberculine. 



PEIPER 8 found that in non-tuberculous subjects it had a con- 

 siderable pyrogenic effect, but was only slightly toxic. Even 

 doses of O'Ol grm. produced only insignificant symptoms, such as 

 pains in the head and limbs, &c. 



All these experiments were put upon a new basis by the fact 

 that the attempts to extract the poisonous substances in an un- 

 altered form from the tubercle bacilli were largely abandoned 

 in favour of experiments with the bacilli themselves. Kocn 9 



1 Nocard, "Des injections revelatrices de la tuberculine," Rec. de Med. 

 Vet., Ixxii., 369; Baumg. Jb., 1895, 705. 



2 Maragliano, "Extrait aqueux des bacilles de la tuberc.," Soc. Biol., 

 l.,94, 1898. 



3 Behring, "BekampfungderTuberkulose," Munch.med. Woch., 1898, 580. 



4 Niemann, "Ueber Tuberkuloseheilserum," Munch, med. Woch., 1897,59. 



5 Gramatschikoff, " Ueber einige physiolog. Wirk. des kochschen Tuber- 

 kulins," Arb. pathol. List. Tubingen, i., 287; Baumg. Jahrb., 1897, 548. 



6 v. Lingelsheim, "Ueber die Wertbestimmung der Tuberk. Giftpra- 

 parate," Deutsch. med. Woch., 1898, 583. 



7 Carriere, "Etude exper. des alterations histolog. du foie, &c.," Arch. 

 Med. Exper., ix., 65, 1891. 



8 Peiper, "Ueber die Wirkung des Kochschen Mittels auf Gesunde," 

 Deutch. med. Woch., 1891, 160. 



9 R. Koch, "Ueb. neue Tuberkulinpraparate," Deutsch. med. Woch., 

 1897, 209. 



