78 PROTEIN POISONS 



melting-point, but begins to melt at 194 to 195. Hender- 

 son collected samples melting from 190 to 200, prepared 

 by different individuals from widely different sources. 

 By careful purification he obtained from each sample a 

 product melting at 192 or 193. Thus it would appear 

 that the apparent discrepancy in the melting-point is due 

 to impurities. Reactions, crystalline form, properties, and 

 melting (or decomposing) show that the picrate and chloride 

 from the germ are identical with lysin picrate and chloride 

 from gelatin and from fibrin. Thus the presence of one of 

 the hexon bases in the bacterial cell has been demonstrated, 

 and another point of resemblance between bacterial and 

 other proteins has been established." 



Mono-amino- acids. The phosphotungstic acid filtrate ob- 

 tained by Leach in her work on the hexon bases was turned 

 over to Wheeler, who has made the following report on it: 

 "From the solution phosphotungstic acid was removed 

 with barium hydrate and carbon dioxide used to remove 

 excess of barium. By concentration and crystallization 

 bodies were obtained resembling tyrosin and leucin under 

 the microscope. These were purified by repeated recrystal- 

 lization from water or from ammoniacal water, the tyrosin 

 being so much less soluble than the leucin that they could 

 be separated by difference of solubility. It was necessary 

 to boil the leucin fraction with animal charcoal to remove 

 the coloring matter. The tyrosin formed the characteristic, 

 colorless, silky needles, many grouped in the characteristic 

 sheaves. As it became more pure the needles were longer 

 and longer, and grouped in the sheaves less positively. 

 After many purifications the crystals melted at a constant 

 temperature, though this was difficult to determine, since 

 tyrosin melts with decomposition. The melting-point 

 maintained after each of two or three recrystallizations 

 was 288, uncorrected. The correction was 8.13, which 

 made the corrected point 296.13. A Kahlbaum prepara- 

 tion of tyrosin in the laboratory melted within a degree of 

 the same point, and agreed in the chemical tests, to be 

 mentioned presently. Richter gives the melting-point of 



