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 I -25 to 3.75/i in length, and about •6|« 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 1.611 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/* in diameter ; zoogloea forms are also very 

 numerous. 



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

 but gives rise to no zoogloea 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 1.65/1 in length and .4;j 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/j in breadth. 

 j8. Bacilli at most i/i in breadth. 



a. Bacilli 2. 5/« 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 ftom 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, lo/t in length and 2.5/t in thickness; the ends are somewhat 

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

 contents are frequently granular. 



j3. Bacilli at most l/t in breadth. 

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

 ii. No Clostridium forms, see p. 432. 



