GENERAL BACTERIOLOGY 83 



and two-thirds carbon dioxid. These proportions, 

 obtained by the above-described method, are but 

 approximations to the actual condition. Somewhat 

 different results have been reported by Keyes (Jour. 

 Med. Res., 1909, N.S. 16, p. 69). For his experi- 

 ments synthetic media and more precise methods for 

 the control of conditions were employed. 



Gas formation by bacteria does not necessarily 

 depend on the presence of carbohydrates. Nitrogen 

 may be produced from nitrites and nitrates, or urea, 

 hydrogen sulphid, and ammonia from proteins during 

 the process of putrefaction. 



EXERCISE 6. STUDY OF THE GERMINATION OF MOLD 

 SPORES 



Transfer two species of molds from the air plates 

 to slant wort agar and incubate at 37 C. 



After several days, when sufficient growth has taken 

 place, remove spores from the surface of the hyphae by 

 means of a straight needle and suspend these in a tube 

 of liquid beerwort or broth. Transfer a loopful of 

 this suspension to a cover slip and examine under the 

 microscope, magnifying about 600 times. If only a 

 few spores are discovered in a field invert this cover 

 slip over the hollow of a hollow-ground slide and keep 

 in place by painting a ring of vaselin around the hollow. 

 If there are too many spores on the cover slip dilute 

 the suspension with beerwort or broth. This hanging 

 drop is incubated and observed daily under the micro- 

 scope and sketches made of the appearance. In seven 

 to ten days the spores should have produced the whole 

 cycle of development of the mold and new spores 

 should have formed. 



