54 



MEDICAL BACTERIOLOGY 



of pyrogallic acid add 109 Gm. of potassium hydrate dissolved in 145 cc. of 

 water. Should a ground-glass-stoppered jar be used, the ground surface should 

 be anointed with vaseline to insure an air-tight joint, and for the same reason 

 washers are used on screw-top jars. 



Quantity of material to be planted on or in culture media to obtain a growth 

 is governed by a number of factors, among which are the following: 



Some organisms grow luxuriantly when planted on culture media, regardless 

 of whether taken directly from tissue (sputum, 

 pus, blood, urine, etc.) or from previous laboratory 

 cultures; others grow luxuriantly after several 

 transplants from culture media to culture media, 

 but show very scant growth, and that irregularly, 

 when first transplanted from tissue or exudate 

 to culture media; some never grow abundantly and 

 are irregular in growing, no matter how often they 

 are transplanted from media to media and some grow 

 abundantly on certain media and poorly on other 

 media. For these reasons the quantity of any sub- 

 stance planted on media to obtain a culture varies 

 according to the number of organisms contained 

 in the substance, the peculiarities of the particular 

 organism to be cultured and the medium upon 

 which it is planted, also the quantity of growth 

 desired. 



To determine the number of bacteria per 

 cubic centimeter contained in any substance, for 

 the isolation of a single organism from a mixture 

 and for future cultural and biological studies of 

 bacteria, one must obtain a growth in which the 

 colonies remain discrete and far enough apart to 

 permit the removal of a single colony without 

 coming into contact with others 20 to 200 on a 

 Petri dish. 



When dealing with a substance rich in bacteria that grow abundantly 

 as feces containing colon bacilli the almost invisible amount that adheres to 

 a small platinum loop gently touched to it, is sufficient to plant one or several 

 tubes or plates and produce an abundant growth. 



Very many organisms, which ordinarily grow abundantly on numerous 

 media, at times fail to grow at all when transplanted; such failure to grow is a 

 more frequent occurrence when organisms difficult to cultivate are dealt with 

 and hence it is always advisable to plant two, three or more tubes or plates, 

 not one. 



FIG. 9. ARRANGEMENT OF 

 TUBES FOR CULTIVATION OF 

 ANAEROBES BY BUCHNER'S 

 METHOD (MacNeal.) 



