278 APPLIED BACTERIOLOGY 



carefully warmed over a water-bath, is cooled, and mercuric 

 bichloride added, when a somewhat heavy and dense 

 precipitate is formed. This precipitate is carefully washed, 

 and then suspended in water, and sulphuretted hydrogen 

 passed ; the white precipitate is decomposed, with the pro- 

 duction of black sulphide of mercury ; this is then' filtered 

 off. The filtrate is then carefully concentrated by very 

 careful evaporation, until crystallisation begins to take 

 place. All the inorganic salts crystallise out first ; these are 

 removed, and the mother-liquid further evaporated, when 

 needle-like crystals are thrown out of solution. These may 

 be dissolved in water, but they are insoluble in absolute 

 alcohol, ether, benzine and chloroform. The substances so 

 yielded, the ptomaines, may be precipitated by the salts, 

 particularly the chlorides, of the heavy metals. 



These crystals differ very considerably as to their solubility : 

 hydrochloride of putrescin when obtained by the above 

 method separates out in the form of acicular crystals, and 

 on the addition of chloride of gold gives very insoluble 

 crystals of octahedral form, while on the addition of chloride 

 of platinum, octahedral crystals, which are much more 

 soluble, are formed. 



Albumoses, Toxalbumens, etc. — As has already been stated, 

 many of the pathogenic bacteria produce a number of 

 intensely poisonous bodies which are allied in their con- 

 stitution and characters to albumins or proteids. 



Loffler, in 1887, when examining the products of pure 

 cultures of the diphtheria bacillus, found that if a broth 

 culture was freed from the bacilli by filtration through a 

 porcelain filter, and was then injected into a guinea-pig, it 

 gave, rise to the same local reaction and paralytic symptoms 

 as when the bacilli themselves were inoculated. 



Eoux and Yersin isolated the pure albumose by filtering 

 broth cultures of the Elebs-Loffier bacillus through a 



