TEXT-BOOK OF BACTERIOLOGY. 175 



wide-spread network. The effect under the microscope is similar. 

 A close tangle of yellowish-brown threads radiates from the centre 

 outward on all sides ; some larger threads may be easily distin- 

 guished, from which smaller ones proceed. Toward the edge of 

 the colony sonie of these threads are often so thin and transparent, 

 so curiously turned up and apparently ramified, that one might 

 confound them with the mycelium of a mould fungus. 



In gelatin culture the root bacillus offers a very peculiar ap- 

 pearance during the first few days. The puncture is surrounded 

 by large numbers of those processes — those ramified tender off- 

 shoots, so that the whole looks like an inverted fir-tree. In the 

 mean time liquefaction is going on at tlie surface; a dense, moist, 

 gleaming white skin is formed, and under it a cloudy turbidness 

 shows that here too there are large quantities of bacteria. Later 

 on these sink to the bottom, and the culture resembles the ap- 

 pearance described in Bac. subtilis; at the top the crust, then the 

 clear liquefied gelatin, and at the bottom the whitish, crumbly 

 flakes. Yet the pellicle is distinctly different in appearance from 

 that of Bac. subtilis. 



On oblique agar the root bacillus produces — beginning from the 

 inoculation scratch— a grayish-white moist layer, which quickly 

 covers the whole surface. At first this covering also looks like 

 roots, but later on there is nothing of this appearance to be seen, 

 except at the edges, while the middle portion is occupied by a thick, 

 even film. 



On potatoes it grows as a greasy white coating. It is without 

 pathogenic action, even when administered in large quantities. 



Micro-organisms in Milk. 



Unboiled milk is extremely rich in saprophytic micro-organisms 

 of different kinds. The investigations of Lister and Meissner have 

 shown that, like most animal secretions, it is indeed germ-free at 

 the moment it leaves the body, but as soon as it is removed from the 

 mammary gland and comes in contact with the air, with the human 

 hand, or with non-sterilized vessels, bacteria find their way into it. 



Milk being an excellent food for most of the known micro- 

 organisms, we cannot be surprised that they soon begin to multiply 

 very vigorously in it. If we put a few drops of milk, obtained some 

 hours before without special measures of precaution, into gelatin, 

 and spread the latter out on glass plates, a development of numer- 

 ous and various forms soon takes place. Among the rest, there is 

 always one of the hyphomycetes— Oidium lactis— whose colonies ap- 



