100 BACTERIOLOGICAL CHEMISTRY 



acids, being destroyed by boiling with 20 per cent, 

 sulphuric acid but not by 5 per cent. acid. Boiling with 

 sodium hydroxide solutions stronger than 1 per cent, 

 destroyed bios. It was dialysable through semipermeable 

 membranes . 



When yeast was shown to be a rich source of the 

 vitamin-B complex it was thought that bios might be 

 identical with it. This has been shown to be nearly, 

 but not entirely, true, the two complexes having many 

 factors in common. It was soon shown that bios was 

 not a single substance but a mixture of several factors. 

 It was first split into bios I and bios II by the action of 

 barium hydroxide solution, which precipitates bios I 

 but not bios II. Neither fraction alone is active, but 

 mixing them restores the potency of the preparation. 

 Bios I has been shown to be optically inactive meso- 

 inositol. 



Further fractionation has shown that bios contains 

 the following substances : — 



Bios I rne so -Inoaitol 

 Bios Ila Pantothenic acid 

 Bios lib Biotin 

 Bios \ Aneurin 



j3- Alanine 



/-Leucine 



Nicotinic acid 



Pyridoxine. 



Several other substances of known constitution and 

 some of unknown constitution are also involved in small 

 amounts in metabolism. The known substances include 

 adenine, ^-aminobenzoic acid, hsematin, phosphopyridine 

 nucleotides, pimelic acid, riboflavin and uracil. Among 

 the substances of unknown composition are folic acid, 

 the " sporogenes factor " and a fraction from Myco- 

 bacterium, phlei which stimulates the growth of Johne's 

 bacillus. 



The properties of these growth factors will be con- 

 sidered in more detail. 



