140 PRINCIPLES OF BACTERIOLOGY 



material should at least be put in a refrigerator, where cold will both 

 prevent any further growth of some varieties of bacteria and lessen 

 the danger of the death of others. After having made the cultures, 

 some of the infected material should always be smeared on a couple of 

 clean slides or cover-glasses and allowed to dry. These can be stained 

 and examined later, and may give much valuable information. 



In obtaining samples of fluid, such as urine, feces, etc., the bottles 

 in which they are placed should always be sterile, and, of course, no 

 antiseptic should be added. It is necessary to clearly explain this to the 

 nurse, for she has probably been instructed to add disinfectants to all 

 discharges. Disinfected material is, of course, entirely useless for 

 bacteriological investigations. It cannot be too much emphasized 

 that materials which are not immediately used should be sent to the 

 laboratory as quickly as possible, for in such substances as feces, where 

 enormous numbers of various kinds of bacteria are present, those 

 which we seek most, such as the typhoid bacilli, frequently succumb 

 to the deleterious products of the other bacteria present. Even when 

 abundantly present living typhoid bacilli may entirely disappear from 

 the feces in the course of even twelve hours, while at other times they 

 may remain present for weeks. These differences depend on the asso- 

 ciated organisms present, the chemical constitution of the feces or 

 urine, and the conditions under which the material is obtained. 



Not only for obtaining fluid for agglutination purposes, but also for 

 examination for peculiar bodies in the exanthemata, blister fluid is 

 valuable. A blister can be raised quickly by placing a little strong 

 ammonia on the skin and covering with a watch-glass, or more slowly 

 by a caritharides plaster. 



