Microbes in the Static Condition. 17 



employed for the preservation of foods have no other 

 ahn than to protect them against the invasion or the 

 destructive action of these organisms. When these 

 means are defective or powerless to arrest the evolu- 

 tion of the germs which have been deposited there, 

 various changes supervene which diminish the in- 

 trinsic nutritive value of the foods and may even ren- 

 der them detrimental to the health of man or of ani- 

 mals (damaged hay, putrid meat). The contamina- 

 tion of foods by pathogenic germs, properly so called, 

 will be studied later. 



Houses and vehicles. — The walls, floor, and ceiling, as 

 well as the mangers and racks, of houses occupied by 

 animals are constantly liable to receive the germs 

 which are borne in the atmospheric dust, cleansing 

 waters, solid dejections, litter, foods, etc. 



Vehicles (wagons, etc.) serving for the transport of 

 animals may be contaminated by microbes in the same 

 way as houses. 



Havjiess, blankets^ tools, and other objects. — It is easy 

 to understand that these objects will most frequently 

 be contaminated either by the various methods men- 

 tioned above or by their contact with the animal for 

 the use of which they are destined. 



Organism. — After what we have said of the nutrition 

 of germs, we may expect to encounter them in all 

 parts of the economy which are in direct relation 

 with the air, or with solid and liquid media. 



The digestive canal throughout all its course con- 

 tains in large numbers various microbic species which 

 have been carried there by food and drink. In the 

 mouth we find especially a leptothrix, spirochsete, and 

 2 



