oval bodies averaging ia lei gth isJ^ inch, and in breadth ^}oo of an inch. On 

 agar the spores are arranged in long rows, side by side, and are greater m 

 diameter than the cells from which they are derived The earliest appear- 

 ance of spore formation takes place in 41 honrs, at 36° C. (Cheyne), but in 

 some cases it is even sooner. The spores are formed in the centre of the rod, 

 and the formation occurs as follows : The rod begins to swell and become 

 spindle-shaped. Occasionally the swelling is more marked at one end than 

 in the centre. The spindle-shape increases in size, and the centre of the 

 swelling gradually ceases to take the stain. The capsule of the spore is ap- 

 parently formed within the rod and is not merely the outer part of the rod. 

 In three or four honrs the rod is seen to have almost or completely disap- 

 peared, although parts of the faint outline of the ordinary bacillus may be 

 noticed. 



Germination of Spores — Uuder favourable conditions the beginning of 

 the germination of the spores takes place in about three hours. The spore 

 loses its oval shape, becomes elongated, and is soon seen to burst through the 

 spore capsule. It then presents the appearance of a short lod, with a pale 

 envelope embracing one end. The rod gradually leaves the spore capsule, 

 and then goes on multiplying as a full grown bacillus. According to Eisen- 

 berg (39), the spores are decolorized by the tubercle bacilli stain, but prepa- 

 rations may be obtained by using the Ziehl-Nfilsen stain and alcohol for 

 decolorization. The spores also stain by the method of Neisser. 



Polymorphism. — Variations in size and shape may be brought about by 

 growth in acid media, or in media containing different sugars. These varia- 

 tions occur also in the same culture, subjected to exactly similar conditions 

 of growth. 



Involution Forms. — Abnormal forms are especially abundant when the 

 bacillus is grown on blood serum ; peculiar Y-like forms and clubbed shapes 

 are of common occurrence, and relatively few spores are found. 



Biological Oharacters. 



Bouillon — " In meat infusion at the temperature of the body, they 

 grow rapidly, causing muddiness and, after a few days, a slight but not ten- 

 acious scum " (23). In bouillon, with a reaction of -i- .08 (57), at 37° C, 

 there is a slight turbidity in 14 hours, especially noticeable when the tube is 

 shaken. In 24 hours, the liquid is uniformly turbid, with a very fine sedi- 

 ment. In 48 hours, the turbidity increases and a pellicle commences to form. 

 Eeaction of the culture at this time, + .07. After 96 honrs the broth is clear, 

 with a pellicle, white, rather massive, and somewhat tenacious. There is also 

 much sediment. Reaction, after 10 days' growth, — neutral. 



Glycerine Bouillon — Media with original reaction of -1-.08. At 37° C, 

 the bouillon becomes slightly turbid in 12 hours, and quite turbid in 24, with 

 a fine, whitish pellicle on surface, which does not extend to the sides of the 

 tube. If the culture is shaken, the pellicle deposits in flaky masses. The 

 reaction is + 1.2. In 36 hours, the turbidity clears, leaving the media bright, 

 with a smooth, thin, tenacious, and white pellicle on the surface. In many 

 cases the pellicle becomes very wrinkled and greasy-looking. At the end of 

 8 days, the reaction is +2 2, and the bouillon is several shades darker in 

 colour, but quite clear. The reaction after 14 day's growth is -1-4.2. At 

 22° 0. the same changes occur but growth is slower. The bacilli are relatively 

 less numerous than in bouillon and are slightly shorter and thicker. 



Glucose Bouillon. — With a reaction of + 2.0, at 37° 0., the broth is 

 more turbid than plain bouillon after 14 hours' growth ; and in 24 hours, the 



