103 



181 



lene blue, it sometimes appears highly granulated, and thus resembles an extremely 

 small streptococcus. 



Closely related to Mbm. luclicum are apparently the rods Xos. 1 and 2, tiiough they 

 are about normal thickness, and altogether without surface growtiii). In streak cultures, 

 No. 1 (PI. XLIX) is often swollen up to a club shape, and partly Gram negative. They 

 do not reduce nitrate to nitrite, but No. 2 splits up i)eroxide of hydrogen. 



Of the strains of Mbm. lacticum above mentioned. No. (i should be a typical repre- 

 sentative of the acidophile intestinal bacterium Bacillus acidophilus, discovered by Moro'^) 

 and FiNKELSTEiN^). None of the many writers who have studied this GRAM-positive 

 rod have interested themselves in its biology, but have devoted all the more attention 

 to its morphological features, and it has been described, now as a thin form, now as a 

 thick one, now as isolated long rods and again as chains of short segments. As some in- 

 vestigators have observed that it can be very irregular (compare with our No. 1), they 

 go so far as to declare it identical with Bacillus bifidus. This is an excellent instance 

 of what can be attained by morphology alone in bacteriology. As it is quite impossible 

 to determine, from extant literature, what GRAM-positive intestinal bacterium is really 

 meant by Bacillus acidophilus, there is certainly no reason to retain the name. When 

 endeavouring to discover the acidophile fæces bacteria, by enrichment prior to sowing, 

 in sugar broth with ^4 — ^ % acetic or lactic acid, we have either encountered betabac- 

 teria (strains 13, 14, 15, 29 and 30 Were isolated in this way) or microbacteria most nearly 

 approaching strain No. 1. 



Microbacterium mesentericum. This form is, as mentioned, easily recognisable by its 

 enormous mesentery. It is killed by heating to 70°. It is only a weak acid former, and 

 in its relation to the sugars most resembles Mbm. lacticum. It forms long, thin, often 

 highly granulated rods, which, as they lie in slime, appear much thicker in Indian ink 

 preparations than in colour preparations. On AG, where it thrives better than on SG, 

 it looks like a streptococcus (PI. L). 



Mibrobacterium flavum is nearly as resistant to heating as Mbm. lacticum, and like 

 the latter, thrives poorly at anythiijg over 35°. It also grows very slowly below 20°, and 

 has thus only a slight temperature interval for its development. In contrast to the other 

 microbacteria, it will still thrive in a sugar solution containing 10 % common salt. It can 

 form up to 1 % lactic acid from lævulose, but it is only with monosaccharides that it 

 forms any considerable quantity of acid at all. It forms a finely flaked precipitate in 

 broth, and is even more aerobic than Mbm. lacticum. The yellow colour is more strongly 

 apparent on SG than AG. Mbm. jlavum (PI. L) forms clumsy rods, measuring for the 

 most i)art 0.5 X 1—2//, though they can also grow out into threads 10// long. When 

 coloured with methylene blue, it is distinctly granulated. 



Rods such as strain No. 10 (PI. L) are frequent- in calves' dung. Treatment with 

 methylene blue will as a rule only stain the poles, and they are thus easily confused with 

 small micrococci. Although the surface growth is more often white than yellow, and they 

 are only weak acid formers, they are doubtless closely allied to Mbm. flavum. 



M No. 2, however, has now, after 10 years' cultivation, begun to exhibit a slight yellowish-green 

 surface growth, like Nos. 3—6. 



-) Wiener Klin. Wochenschrift 1900, No. 5. 

 'j Deutsche med. Wochenschr. 190Ü, p. 263. 



