I BACTERIA OCCURRING IN SEWAGE 75 



B. capillareus, L, similar, but growing differently. 

 With reference to streptococci, Dr. Houston, in a subsequent 

 eport (July, 1900), describes twenty species or varieties found 

 »y him both in London sewages and in effluents, and says that 

 s a class (i) they are the most pathogenic of all bacteria at 

 present known ; (2) they are delicate germs, and very readily 

 lose their vitality ; (3) they are present in the intestines of 

 animals ; (4) they are absent from water and soil, except where 

 there has been recent contamination with sewage or other 

 objectionable matter. (See also Report of Medical Officer to 

 Local Government Board, 1898-1899.) He considers the 

 search for streptococci a valuable test in the bacterioscopic 

 examination of waters, but it is tedious and uncertain. 



It is obvious that in such a fertile field as raw sewage new 

 species are likely to be continually discovered. 



Organisms in Bacteria Beds. 



The organisms in anaerobic beds are chiefly bacilli, but cocci 

 are not absent. The *' Clostridium forms " are very numerous, 

 meaning such bacilli as develop spores in the middle, so that, 

 owing to the bulging there and tapering of the ends, figures of 

 a distinctly spindle shape are produced. This is characteristic 

 of several species that are obligatory anaerobes, such as Clos- 

 tridium fcetidum, which liquefies gelatine and develops an 

 odorous gas, and C. butyricum, or B. amylohacter. The 

 latter, on account of its importance and its wide distri- 

 bution, requires a special description. Prazmovsky, who first 

 studied its character, found it in almost all animal and vege- 

 table matters decomposing in absence of air, while Nothnagel 

 discovered it continually in faeces. The specific name *' amylo- 

 hacter" [amylum, starch) was derived from its being coloured 

 blue by iodine. It liquefies both albuminoids and carbo- 

 hydrates like cellulose, producing butyric acid and gases, 

 chiefly hydrogen, carbonic acid, and methane. 



The Sutton beds were seeded at first with a culture of 



Micrococcus candicans, obtained by Dibdin from his coke breeze 



filters, but we now know that such seeding is unnecessary, as 



the mixed " flora " of sewage does not allow of the development 



of a pure culture of any specific organism.^ When zonal filters 



are used, a natural differentiation of the organisms occurs. For 



^ Experimental inoculations of the 13-foot coke bed at Crossness with a pure 

 culture of a "sewage proteus," liquefying rapidly, gas-forming, but non-patho- 

 genic, gave " quite negative results." — London County Council Report, 1900, p. 76. 



