188 APPENDIX. 



cavity, which can be closed tip by turning the handle, or opened 

 by turning in the opposite direction. 



It is introduced with the cavity closed, and when it is at the 

 desired depth, the handle is turned, the earth enters the cavity, 

 the handle again turned, incloses it completely, and the borer is 

 then withdrawn. 



The eartli can then be mixed with the gelatine in a tube, and 

 this gelatine then rolled on the walls of the tube after the man- 

 ner of Esmarch, or it can be poured upon a glass plate, and the 

 colonies developed so. 



Another method is to wash the earth with sterilized water, 

 and the water then mixed with the gelatine, as many of the 

 germs are taken up by the water. 



The roll-cultures of Esmarch give the best results, many of 

 the varieties usually found being anaerobic. 



Animals inoculated with the soil around Berlin die almost 

 always of malignant oedema, and with that of some other towns 

 invariably of tetanus. Many of the germs found are nitrogen 

 formers and play a great role in the economy of the soil. 



Nitrifying organisms are found in the superficial layers of the 

 earth. Organic matters found in sewage and in the faecal evac- 

 uations of animals form the basis for their activity, whereby 

 nitrates, ammonias, and nitric acid result. The nitrogen neces- 

 sary for the growing plant is thus produced. The nitro-monas 

 of Winogradsky belongs to this group. 



The Bacteria of Milk and Other Foods. Milk as secreted is 

 sterile, but at every step in its passage from the cow to the con- 

 sumer it is liable to contamination. Even the lower portion of 

 the teat is a source of infection, owing to the presence of stagnated 

 milk from the former milking, and, as consumed, milk usually 

 contains thousands to millions of bacteria to the cubic centimetre. 

 Sterilization or Pasteurization and supervision of the dairies 

 should always be carried out on milk used for infant feeding. 



Foods eaten after little or no cooking, such as fruits, salads. 

 and the like, and also oysters, are possible sources of bacterial 

 diseases, and the not infrequent so-called ptomaine poisoning 

 observed after the consumption of ice-cream, sausage, canned 

 meats, etc., is the result of the action of bacteria or their 

 products 



