HEHANIUL'R OF 1:A( TKRIA. ,V ' 



• 



might be educated u]) to tolerance for somewhat higher concen- 

 trations. Neither oxidation of arsenite nor reduction of arsenate 

 was shown by any of the species examined. In this connection 

 it may be recalled that B. arsenreditcens, which tolerates over 

 1 per cent, of As.X).^ as arsenite and reduces arsenate with oreat 

 vigour, has the group number 222.2333033, and falls into the 

 typhosus branch of the colpn family. Its existence therefore 

 ))recludes any generalisation concerning the tolerance of the 

 group towards arsenite, although it is apparent that the family 

 as a whole is intolerant. The resistance towards arsenate is 

 much greater than towards arsenite. 



(3) Putidum (jroup: B. pyocyaiiciis, B. fiiioresccns liqnifa- 

 ciois, B. flnorcscens iioji'liqiiifaciens, and a non -fluorescing 

 variety isolated from tank di]). All proved highly tolerant of 

 arsenite. The strains of ftuorcscens non-Uqiilfaciens isolated 

 from tank dip were capable of growing freely in i per cent, 

 arsenite bouillon, and were not completely sup])resse(l by 1 .5 per 

 cent. With B. pyocyancns inhibition of growth was noted at 0.5 

 ])er cent., but by subcultivation into media of gradually increasing 

 concentration a t(jlerance for i per cent, arsenite was established. 

 wStill higher concentrations of arsenate j^enuitted of free growth. 

 Although highly tolerant tow'ards arsenic, neither oxidation of 

 arsenite nor reduction of arsenate was effected. 



(4) Miscellaneous imperfectly-yronped organisms: 



(a) Cocci. Two chromogenic cocci, probably M. roseus and 

 M. aurantiacus^ showed a low tolerance for arsenite, being in- 

 hibited by the presence of o. i per cent, in bouillon. 



A coccus 2i2.;^2i2>?)'^'^2)' about .5/x in diameter, isolated from 

 cattle faeces, was found to grow freely in 0.2 per cent. As.( ).. as 

 arsenate in bouillon, but to be inhibited b)- 0.05 ])er cent, 

 As^>0.^ as arsenite. A similar non-chromogenic coccus, isolated 

 from cattle dip, w^as found capable of tolerating ten times thi- 

 concentration of arsenite — 0.5 i)er cent. As^C).,. 



{b) Sarcina: A yellow sarcina 221.3332523, isolated from 

 laboratory air, and probably an atypical sarcina tlava, coukl 

 tolerate o.i per cent. As^^O.^ as arsenite bouillon; but not 0.2 |)er 

 cent. 



(c) Bacteria: A yellow bacterium, isolated from :i jilate 

 exposed to stable air, grew easily in 0.2 per cent As^( )., as 

 arsenate, but was inhibited by 0.05 i)er cent, as arsenite. Precise 

 identification w^as not possible without a com|)arative collection. 

 but the organism may be briefly described. Group number 

 211.3332613: polymorphic rods about .3/x in breadth and .7". 

 to 2fi in length. Non-motile and Gram-negative, lirowth la] id, 

 colonies on agar reaching 2 mm. in 48 hours, and extending to 

 4 mm. in the course of a w-eek ; colonies round, with entire edges 

 and amorphous interior, (irowth on agar slo])es light tran.sparent 

 yellow, keejjing closely to the track of the loo]); later becoming 

 light transparent orange, smooth, shiny, and viscid ; finally deve- 

 loping a brown tint. Strongly proteolytic ; stratiform liquefac- 



