METHODS OF EXAMINING EARTH 85 



fsecal evacuations of sea fowls in the saltpetre beds of Chili and Peru. 

 It is largely by means of these organisms that growing vegetation 

 obtains the nitrogen necessary for the nutrition of its tissues. Special 

 cultivation media are necessary for the growth of these organisms. 



WINOGRADSKY'S METHOD. 



For preparation of the special media used, see Preparation of 

 Media ( 105, p. 57). 



1. Inoculate one of the flasks with a little of the soil to be investi- 

 gated. 



2. In four or five days withdraw with a sterile pipette some of 

 the solution from the above flask from over the surface of the layer of 

 magnesia carbonate, and transfer to a second flask No. 2. 



3. Change again some material from flask No. in four or five 

 days to a third flask, continue the changing process until ultimately 

 the nitrifying organisms flourish as almost transparent films attached 

 to the granulated magnesium carbonate at the bottom of the flask. 

 The organism is known as the Nitromonas. 



CLVIL POINTS TO BE OBSERVED IN DESCRIBING AN 

 ORGANISM (ABBOTT). 



1. Its source as air, water, or soil. If found in the animal body, 

 is it normally present, or only in pathological conditions ? 



2. Its form, size, mode of development, occurrence of involution 

 forms, or other variations in morphology. Grouping, as in pairs, 

 chains, clumps, zoogloea; presence of capsules; development and 

 germination of spores ; arrangement of flagella. 



3. Staining peculiarities especially its reactions with Gram's 

 (or Weigert's fibrin) stain, and peculiar or irregular modes of staining. 



4. Motility to be determined on very fresh cultures and on 

 cultures in different media. 



5. Its relation to oxygen Is it aerobic, anaerobic, or facultative ? 

 Does it develop in other gases, as carbonic acid, hydrogen, etc. 



6. Both the macroscopic and microscopic appearance of its 

 colonies on nutrient gelatine and on nutrient agar-agar. 



7. The appearance of its growth in stab and slant cultures on 

 gelatine, agar-agar, blood serum, and on potato. 



8. The character of its growth in fluid media, as in bouillon, 

 milk, litmus milk, rosolic acid, peptone solution, and in bouillon 

 containing glucose. 



9. Does it grow best in acid, alkaline, or neutral media ? 



