S6 



PHYSIOLOGY OF NUTRITION 



water is thus used in bacteriological laboratories. The hands of the worker and 

 also his implements are disinfected with this solution, which is also employed to 

 destroy cultures that are not needed. A solution of one part of the salt in 

 300,000 parts of water prevents the development of the bacillus of splenic 

 fever, 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 car- 

 bolic acid, are also suitable for use as disinfectants." 



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

 mental history and their physiological processes it is necessary to obtain them 



in pure culture.^ 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 ceU. 

 A culture in which all the microorganisms 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 physiological 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 micro- 

 organisms 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 developmental 

 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. 



Fig. 35. — Autoclave. The top 

 is hinged and may be raised after 

 releasing the locking clamps. 



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

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

 Berlin N, Seestrasse 6s; Jorgensens Laboratorium, 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.\ 



"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 ma> be useless or even harmful in others. 

 Numerous references on this subject are given in the Index Medicus, Carnegie Inst., 

 Wash.— £rf. 



