io AIDS TO BACTERIOLOGY 



growth, C. Russ (Proc. Roy. Sor,., 1909, p. 314) shows 

 that under the influence of a suitable current certain 

 bacteria aggregate at one or other electrode, and uses this 

 action for the collection of bacteria from a fluid medium. 

 Thus, if sodium chloride be used, nearly all go to the 

 positive electrode, a large number being killed. It is 

 suggested that successful ionisation of suppurating wounds 

 is effected by drawing the bacteria out of the tissues and 

 then exposing them directly to the destructive effect of the 

 electric current. 



Products of Metabolism in Bacteria. The action of 

 bacteria on the surrounding medium is generally of an 

 analytical nature, complex nitrogenous substances and 

 carbohydrates being decomposed into simpler substances 

 Jordan attempts to classify the chemical products of 

 bacteria under the following heads: (i.) The secretions or 

 substances which subserve some purposeful end in the cell 

 economy; (ii.) the excretions or substances ejected because 

 useless; (iii.) the disintegration products formed by the 

 breaking down of food substances; and (iv.) the true cell 

 substance. The word ' aporrhegma ' has been applied 

 to any substance split off by biological actions, but its 

 employment is not encouraged by the precise. 



Production of Heat. Bacteria of thermophilic character 

 are responsible for self -heating of hay and some forms of 

 spontaneous combustion, especially the firing of moist 

 cotton. 



Photogenesis. Phosphorescence, especially that seen on 

 fish, is often due to bacteria. The photogenic bacteria 

 are generally, but not always, of marine origin. 



Some bacteria produce a fluorescence in the culture 

 medium. 



Chrom,ogenesis. A number of bacteria produce pigments, 

 often lipochromes. The raison d'etre of these pigments is 

 uncertain, but probably they are excretory products of no 

 service to the organism. B. prodigiosus produces a red 

 pigment. On one occasion it contaminated a water-supply 

 and infected the bread made with it. The same organism 

 is the causative agent of the ' bleeding host.' Chromidrosis 

 (coloured sweat) is attributed to bacteria. While the term 

 ' chromogen ' is restricted to bacteria that produce a pig- 

 ment either for retention in their cells or for excretion, 

 many others produce a pigment or change of colour in 



