76 MICROBES AND TOXINS 



a diastase of the fungus ; three parts by weight of sugar furnish 

 about one of growth. When glucose is supplied instead of 

 saccharose, the culture starts off more quickly ; lactose is not a 

 good food-stuff. Alcohol (in quantity equivalent to the weight 

 of sugar) interferes with the germination of the spores, but in 

 the adult form the fungus gets on quite well with it ; alcohol 

 is thus a poison to the embryo, but good food for the adult. 

 Starch paste (boiled) can supply the necessary carbohydrate 

 nourishment, but raw starch alone prevents germination ; the 

 adult would, however, attack it as a sort of last resource. 



The Bearing of Raulin's Experiments. These are 

 not mere laboratory fantasies but are in reality almost the first 

 exact experiments on the conditions of plant cultivation and 

 growth. For every plant in the fields, for every microbe in the 

 laboratory, a Raulin's fluid is demanded, a fluid which would 

 represent ideal conditions for development : all the improve- 

 ments in the technique of cultivation are attempts in this 

 direction. For example, the first cultures of the tubercle 

 bacillus were made with great difficulty on coagulated blood 

 serum : good growth was only obtained by adding glycerine to 

 the nutritive medium (Nocard and Roux). Almost all our 

 culture media for bacteria are empirical : blood, ascitic fluid, 

 and serum are supplied to them because we know that they 

 live well in the animal body in these fluids. If our knowledge 

 of bacteria was as far advanced as is that of Aspergillus it 

 would be possible to make media of known and constant 

 composition with measured quantities of the constituents, and 

 these would undoubtedly be of the greatest value in the 

 preparation of vaccines and toxins. When we consider that 

 Aspergillus is sensitive to zinc in the dilution of i in 50,000 

 and to silver nitrate in the proportion of i in 1,600,000, it is 

 possible to foresee to some extent the solution of many 

 technical difficulties and to appreciate the extent of what 

 remains to be discovered in connection with the action of 

 manures, food-stuffs and drugs. Raulin's experiments show to 

 what degree bacteriology and medicine depend on the progress 

 of chemistry. 



