Bacillus alvei. By Messrs, F. Cheshire ct Watson Cheyne. 597 



the Microscope. I shall now describe the characteristics of the 

 Bacillus alvei when cultivated in these three modes. 



a. Test-tube cultivations. — If an infected needle be plunged 

 into a tube of gelatinized meat infusion, in the manner described 

 above, growth occurs both on the surface and along the needle-track. 

 On the surface the bacilli shoot out in all directions from the point 

 of entrance of the needle, forming a delicate ramifying growth on 

 the top of the gelatin ; the characteristics of this growth will be 

 presently described under h. Along the track whitish irregular- 

 shaped masses appear, which slowly increase in size and run 

 together. In a few days processes are seen to shoot out from these 

 masses, which may extend through the gelatin for long distances 

 from the track, being thickened at various parts and clubbed at the 

 ends. These processes do not appear to join one another at their ends 

 (see figs. 5 and 6). A very beautiful and characteristic appearance is 

 got where very few bacilli are introduced with the needle and where 

 therefore at various parts of the track, more especially at the lower 

 part, individual bacilli or groups of bacilli are planted at a consider- 

 able distance from each other. In a few days minute round whitish 

 specks become visible to the naked eye. These increase in size till 

 in about ten days shoots begin to appear. These radiate from the 

 central mass in all directions and become nodular at various parts 

 as described above. When such a cultivation is old the white 

 branches disappear, and only little whitish collections of bacilli 

 are seen at various parts. On examining such a tube with a pocket 

 lens, however, numerous watery-looking tracks are seen running 

 through the gelatin from the central mass to the whitish collec- 

 tions. The gelatin at the upper part of the track generally 

 evaporates, to some extent giving rise to the air-bubble appearance 

 so characteristic of the cholera bacillus (see fig. 6). 'lliese are 

 the appearances seen where the material contains gelatin in the 

 proportion of 10 per cent. Where less gelatin is present the 

 naked eye appearances, while possessing the same characteristics, 

 are somewhat different. The shoots are much more numerous and 

 appear much more rapidly, giving rise to a haziness around the 

 needle track which with the pocket lens is seen to consist of 

 numerous dehcate branches clubbed at the ends a'^ in the former 

 case. I think the amount of peptone present also makes a difference 

 in the appearance, though of tliis point I am not yet absolutely 

 certain. The most characteristic growth is, however, obtained 

 when the material contains 3 per cent, peptone as well as 10 per 

 cent, gelatin, the shoots being then less numerous and much 

 coarser. And I can easily understand that this would be the case. 

 for the bacilli would have a large supply of nutriment in their 

 immediate vicinity without the necessity of having, so to speak, to 

 spread out through the gelatin in search of foorl, as may bo the 

 Scr. 2.— Vol.. V. '^ 11 



