152 PTOMAINES AND TOXALBUMINS, 
one per cent of peptone and four to five per cent of glycerin have 
been added. This culture liquid is placed in flasks and inoculated 
upon the surface with small masses from a pure culture of the tu- 
bercle bacillus. A tolerably thick and dry white layer is developed, 
which after a time covers the entire surface. At the end of six to 
eight weeks development ceases and the culture liquid is evaporated 
over a water bath to one-tenth its volume ; this, after being filtered, 
constitutes the crude tuberculin. By precipitation with sixty-per- 
cent alcohol Koch has obtained from this a white precipitate which 
has the active properties of the glycerin extract. This is soluble in 
water and in glycerin, and has the chemical reactions of an albumi- 
nous body. 
Zuelzer has (1891) reported his success in isolating a toxic sub- 
stance from tubercle cultures. The contents of tubes containing 
pure cultures of the bacillus are first treated with hot water 
acidulated with hydrochloric acid. This solution is filtered, evapo- 
rated, and then several times precipitated with platinum chloride. 
The double salt formed is decomposed by hydrosulphuric acid, 
after which the liquid is filtered and evaporated to dryness. <A 
white, crystalline salt is thus obtained which is soluble in hot water. 
This salt was toxic for rabbits and guinea-pigs in doses of from one 
to three centigrammes. Death usually occurred in from two to four 
days. In guinea-pigs one centigramme injected subcutaneously 
caused, within a few minutes, a greatly increased frequency of respi- 
ration, an elevation of temperature, and protrusion of the eyeballs. 
Mallein.—Kalwing, Preusse, and Pearson have obtained from 
cultures of the glanders bacillus a “‘lymph” which somewhat re- 
sembles the crude tuberculin of Koch. This was obtained by 
Preusse by treating old potato cultures of the glanders bacillus with 
glycerin and water. The extract was filtered several times and then 
sterilized in a steam sterilizer. This lymph injected into horses in- 
fected with glanders gives rise to a very decided elevation of tempe- 
rature, while in horses free from this disease no such result follows. 
