THE BIOLOGICAL ACTIVITIES OF BACTERIA 69 



to these absorption bands, the bacteriopurpurin of the red sulphur 

 bacteria shows absorption of the invisible ultra red rays of the 

 spectrum. 



Engelmann, with a microspectroscope, projected a spectrum into 

 a microscopic field in which green algae or, in the case under discus- 

 sion, red sulphur bacteria had been placed. Other sources of light 

 were, of course, excluded. By adding emulsions of strictly aerobic 

 bacteria to such preparations, an accumulation of microorganisms 

 was observed at those points in the spectrum at which most oxygen 

 was liberated. In the case both of chlorophyll and of the red sul- 

 phur bacteria such areas of bacterial accumulation (in oxygen 

 liberation) occurred in the zones of the absorption bands mentioned 

 above. 



THE SO-CALLED ' ' BACTERIOPHAGE ' ' PHENOMENON 



During the last few years a phenomenon has been observed with 

 bacteria which is likely to be of fundamental importance in the 

 biological and immunological study of bacteriology. 



The first observation upon this curious phenomenon was pub- 

 lished by Twort in 1915. 3 * Twort was engaged in a search for a 

 non-pathogenic filtrable virus on the very logical assumption that 

 the few pathogenic filtrable virus which had been associated with 

 a number of diseases probably represented isolated members of a 

 large kingdom of microorganisms. His cultural and animal studies 

 proving negative by the ordinary methods, he carried out experi- 

 ments with glycerinated calf vaccine which he cultured on agar 

 tubes. After variable periods of incubation such agar slants would 

 exhibit watery areas and in those cultures in which micrococci grew, 

 it was found that some of the colonies could not be sub-cultured, 

 but if preserved, the originally normal culture would become glassy 

 and transparent. Smears made from these glassy areas showed red- 

 dish staining granules by Giemsa. Plating of the condensation water 

 of such slants resulted in colonies which usually after preservation 

 became transparent, starting unlike most degenerative processes, 

 from the edge of the colony. Pure cultures of pneumococci and 

 other microorganisms when touched with small portions of the glassy 

 colonies would become transparent at the point touched and this 



84 Twort, Lancet, December 4th, 1915. 



