428 APPENDIX. 



even dark brown or black ; on agar-agar is seen as a similar growth, which, 

 however, is somewhat grey in colour, and the green is never so well made 

 out as in the early gelatine cultures ; on potatoes it forms a yellowish 

 layer near the point of inoculation, the surrounding potato being stained 

 greenish blue ; on blood serum it gives rise to no coloration ; is an aerobic 

 and exceedingly motile bacillus from i to 4ft in length and .3 to .^fi in 

 breadth with slightly blunted or, if spores are being formed, club-shaped 

 ends, though very frequently spores appear to be formed in the middle of 

 the organism also ; in alkaline milk gives rise to a slate colour, but if grown 

 in the presence of lactic acid to an intense blue ; this colour is most freely 

 developed at from 15° to 18° C, at 37° C. no colour is formed at all. 



y. The substratum is stained violet, 

 (l) Bacillus janthinus (Violet bacillus). — Differs from the bacillus 

 violaceus which liquefies gelatine. (Grows very slowly, and later causes 

 liquefaction of the gelatine. ) It was first found in water ; when grown 

 on gelatine, milk white points appear, which later become violet, espe- 

 cially at the margins ; the surrounding gelatine also becomes deep violet, 

 but the organisms only develop the colour where there is a free supply of 

 oxygen ; in this case, as in the last, the colour is probably formed through 

 the breaking down of the proteid ; under the microscope the organism is 

 found to consist of motile rods, some longer some shorter, but these 

 gradually break up into shorter lengths. 



c. Colonies are cream coloured. 



(1) Bacillus of septic pneumonia. — Poels has described an organism 

 as occurring in septic pneumonia of calves. It is a short rod-shaped 

 organism with a constriction in the middle, which gives it the appearance 

 of a diplococcus ; grows on gelatine as a rough layer ; forms small rounded 

 colonies around the point of inoculation, which gradually run together ; 

 along the track of the needle in puncture cultures small rounded whitish or 

 cream coloured colonies are formed ; on agar-agar it forms a shining 

 smooth layer exceedingly thin and sharply defined in from 10 to 15 

 hours ; on sterilized blood serum forms a creamy layer similar to that 

 already described, and on the surface of sterilized potatoes spreads over 

 a large area ; kills rabbits, guinea-pigs, mice, calves, pigs ; sheep and 

 dogs not affected, Poels thinks that it is closely allied to the mouse 

 septicaemia group of bacilli. 



D. Colonies of a yellow colour, 

 (i) Bacillus luteus. — Forms in the superficial layer of gelatine plate 

 cultivations small yellowish points 2 to 3mm. in diameter, often of a light 

 brown colour with a whitish translucent margin ; deeper down they are 

 much smaller, are usually the shape of a lentil, and can only be made 

 out with the aid of a microscope, when they appear to be irregular in out- 

 line and of a brown colour ; a yellowish growth is formed along a surface 

 needle track ; it is a short non-motile bacillus of medium thickness. 



(2) Bacillus fuscus. — Obtained from a putrefying infusion of maize, and 

 also foiind as an accidental impurity in certain cultures. Quickly forms, 

 rounded brownish colonies ; deeper it forms dark brown nodules sur- 

 rounded by a highly refractile border ; at the surface of puncture cultures 

 it usually forms a wrinkled brownish red deposit around the point of 

 entrance of the needle. The organism is a motile rod. 



