ASSIMILATION OF CARBON 



59 



Bacillus anthracis. Sulphurous acid, chlorinated lime [also known as bleaching 

 powder; it contains calcium hypochlorite], hydrofluoric acid and its salts, boric 

 acid, ozone, hydrogen peroxide, milk of lime, and phenol, or carbolic acid, 

 are also suitable for use as disinfectants. e 



§6. Pure Cultures. — To study microorganisms with respect to their de- 

 velopmental history and their physiological process it is necessary to 

 obtain them in a pure culture. 1 A pure 

 culture is one known to contain only a single, 

 definite species of organism. Such a culture 

 can be obtained only by fulfilling two conditions. 

 The first consists in the exercise of sufficient 

 precaution to prevent the entrance of germs 

 from the air into the sterilized culture medium; 

 the second is the derivation of the culture from 

 a single cell. A culture in which all the micro- 

 organisms are quite similar is nevertheless not 

 to be termed a pure culture unless it has been 

 derived from a single cell, since very many 

 microorganisms with entirely different phy- 

 siological properties have exactly the same form. 

 On the other hand, a culture obtained from a 

 single cell is called a pure culture, even though 

 the microorganisms therein contained exhibit 

 diverse forms, since we now know that one and 

 the same species of bacterium or yeast can 

 assume different forms, according to its devel- 

 opmental stage and the influence of the medium 

 in which it is grown. 



The method most frequently used for the 

 production of pure cultures is that of dilution. 

 This method was first used, in its original form, by Lister 2 in 1878, to obtain 

 a pure culture of lactic acid bacteria. It was carefully elaborated for yeasts 

 by the Danish bacteriologist, Hansen in 1881/ 



1 Pure cultures may be purchased from several establishments, among which may be mentioned the 

 following: Krals Bakteriologisches Laboratorium, Prag I, Kleiner Ring II; Institut fur Garungsgewerbe, 

 Berlin N, Seestrasse 65; Jorgensens Laboratrium, Kopenhagen, Frydendalsvej 30; Zentralstelle fur Pilz- 

 kulturen, Amsterdam. [They may be obtained from the Laboratory of the American Museum of Natural 

 History, New York, and from Parke, Davis and Co., Detroit. — Ed.] 



2 Lister, Joseph, On the lactic fermentation and its bearings on pathology. Trans. Pathol. Soc. London 

 29: 425-467. 1878. 



e To the substances mentioned in the text may be added: iodine, sodium sulphite and 

 Dakin's recent discovery, paratoluene-sodium-sulphochloramide (on the American market 

 under the trade-name chlorazene, though it was called "chloramine" by Dakin [British 

 med. jour., Aug. 25, 1915, also Jan. 29, 1916]). Chlorine, bromine, and potassium per- 

 manganate are also used as disinfectants. It should be noted, however, that antiseptics 

 or disinfectants that are useful in some cases may be useless or even harmful in others. Num- 

 erous references on this subject are given in the Index Medicus, published by the Carnegie 

 Institution of Washington, Washington, D. C. — Ed. 



! Hansen, 1896. [See note 1, p. 45.]. — Ed. 



Fig. 35. — Autoclave. The top 

 is hinged and may be raised after 

 releasing the locking clamps. 



