APPENDIX. 431 



gradually becomes covered with these motile colonies, and then liquefaction 

 takes place rapidly ; this is completed at the end of forty-eight hours. 

 There is a foul odour and a marked alkaline reaction ; in the track of the 

 needle in pure cultures colonies may be seen which have a peculiar radiate 

 formation, the liquefaction always extending wherever these colonies appear. 

 Liquefaction takes place more slowly when oxygen is cut off; short ciliated 

 rods and threads r25 to 3.75/1 in length, and about '6/1 in thickness. The 

 threads are usually twisted and convoluted ; grows at about 20 to 24 cc., 

 and causes very rapid liquefaction of the gelatine ; no spore formation ; in- 

 volution forms are found spherical bodies, about l.6/i in diameter; is 

 pathogenic. 



(2) Proteus mirabilis. Something like the preceding organism, but 

 liquefies the gelatine much more slowly. (No liquefaction takes place 

 when oxygen is cut off.) The threads are much longer, and the colonies 

 have a finely granular brownish appearance under the microscope, espe- 

 cially towards the centre ; the organism is about the same thickness as the 

 above, but may be somewhat shorter ; distinguished especially by the fact 

 that spherical or pear-shaped involution forms are more frequently met with, 

 these being from 3.75 to 7/j in diameter ; zooglcea forms are also very 

 numerous. 



(3) Proteus Zenkeri. In plate cultures forms thick whitish-grey layers, 

 but gives rise to no zooglcea forms ; in gelatine tubes a thick layer is formed 

 at the point of inoculation, which by regular steps becomes thinner towards 

 the periphery ; from the margin threads shoot out ; at the end of twenty- 

 four hours there are large moving islands similar to those already examined, 

 but liquefaction only takes place immediately at the surface, the deposit 

 gradually becoming thicker and more opaque ; the long thread forms are 

 seldom met with ; the bacilli are 1.65^ in length and .4/1 in breadth, or 

 they may be more rounded, or even a little longer ; they are motile. 

 (Although classed with the liquefying organisms, this liquefaction is some- 

 times so slight that it can scarcely be made out.) There is little or no 

 odour given off from gelatine or blood serum cultures, but there is a strong 

 smell given off when the organism is cultivated in meat infusions. 



b. Colonies circumscribed without branches. 

 a. Bacilli 2-5/t in breadth. 

 /3. Bacilli at most i/* in breadth. 



a. Bacilli 2.5/1 in breadth. 



(i) Bacillus megaterium. First found on boiled cabbage-leaves. 

 Occurs on plates as small round liquefying colonies ; grows on gelatine 

 very rapidly, liquefying in a funnel shape from the surface downwards ; 

 develops as a whitish layer on agar-agar, the surrounding material becoming 

 somewhat darker ; grows rapidly on potatoes at 20 C., as yellowish-white 

 cheesy points near the seat of inoculation ; proliferates by transverse division 

 and by end spores ; distinctly an aerobic organism ; occurs as slightly bent 

 motile rods, io/t in length and 2.5/4 in thickness; the ends are somewhat 

 rounded ; sometimes form chains of from two to ten bacilli. The cell 

 contents are frequently granular. 



jS. Bacilli at most i/t in breadth. 



i. Development of clostridium forms before spore formation, see p. 432. 

 ii. No clostridium forms, see p. 432. 



