Bacillus alvei. By Messrs. F. Cheshire d' Watson Cheyne. 599 



growth. The forms assumed are the most beautiful shapes 1 have 

 ever seen, but they are very numerous, always however retaining the 

 tendency to form curves and circles ; thus we have the explanation 

 of the appearances previously described in the test-tube cultivations. 



c. The appearances of the colonies on plates on which the 

 mixture of bacilli and gelatinized infusion has been poured out is also 

 very characteristic. The earliest appearance of colonies is a small 

 oval or round group of bacilH. This group is not homogeneous in 

 appearance under a low power of the Microscope, but lines indicating 

 the bacilli are seen in it. It very soon becomes pear-shaped, and 

 from the sharp end of the pear processes begin to pass out into the 

 gelatin, as before described. (See fig. 1'2.) 



These bacilli do not grow below 16" C. The best growth in 

 gelatin is obtained at a temperature of about 20^ C. They grow 

 most rapidly in cultivating materials kept at the body temperature. 

 Very few spores are formed at the lower temperatures, but they 

 appear rapidly and in large numbers at the body temperature. I 

 have several times observed bacilli containing spores swimming 

 about freely. The reaction of the medium is not of any very great 

 importance, but a neutral medium is apparently the best. The 

 bacilli swim freely in fluids with a slow oscillating movement. 



They grow readily at the body temperature in meat infusion 

 with peptone and rendered solid by agar-agar, but the appearance 

 of their growth is not nearly so characteristic as in gelatin. This, 

 indeed, is the case with most bacteria, so that agar-agar preparations, 

 though very useful for carrying on pure cultivations at the tem- 

 perature of the body, are of little value for diagnostic purposes. 

 They grow most rapidly on the surface of the agar-agar, forming a 

 whitish layer, but the shoots described above in the case of gelatin 

 do not occur, or only very imperfectly, in agar-agar. Here the 

 bacilli arrange themselves apparently side by side, and, producing 

 spores in this position, we have as a result, after a few days' 

 cultivation, long rows of spores lying side by side with here and 

 there an adult bacillus. (See figs. 10 and 11.) 



On potatoes they grow slowly, forming a dryish yellow layer 

 on the surface. They grow very slowly indeed at the lower tem- 

 perature. In order to get good growth it is necessary to keep the 

 potato at the body temperature. 



In milk they grow well at the body temperature, and in a few 

 days cause coagulation of the milk, which also as^^umes a yellowish 

 colour and gives off the odour previously descril>ed. The coagulum 

 is not firm, like that caused by the Bacterium lactis, but is like a 

 tremulous jelly, and may remain for a considerable time without 

 the separation of any fluid, but ultimately it becomes liquid, and 

 after some months assumes the appearance of a dirty, brownish- 

 yellow, glairy fluid. It is very slightly, if indeed at all, acid. 



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