36 STUDY AND IDENTIFICATION OF BACTERIA. 



from the differences in deep colonies that the greatest difficulties in the 

 study of bacteriology arise. By using the method of simply stroking 

 plates along five or six parallel lines from one side of the plate to the 

 other with a glass rod, loop or swab, we obtain colonies which are well 

 separated and which are entirely superficial. 



The material as pus, feces, throat membrane, etc., should be evenly 

 distributed in a tube of sterile water or bouillon; the swab which was 

 originally used for obtaining the material being then pressed against 

 the sides of the test-tube to express excess of fluid and then stroked 

 gently over successive lines on one plate. Or, if the organisms be 

 very abundant, over a second plate without recharging it from the 

 inoculated tube. 



To obtain isolated colonies on blood-serum or blood-streaked agar, 

 which can be touched and by transfer obtained in pure culture, we 

 simply smear the material on a slant of either medium. Then, without 

 sterilizing the loop, we smear it thoroughly over a second slant, and so on 

 to a third, or possibly a fourth or fifth. 



At present the classification of the bacteria is very unsatisfactory 

 from a scientific stand-point. The nomenclature abounds in instances 

 where three or four terms are used in naming a single bacterium, in- 

 stead of the single generic name and single specific one as is used in 

 zoological nomenclature. This matter of nomenclature is a subor- 

 dinate factor in the confusion when we begin to investigate and find 

 that different names have been applied to apparently the same organ- 

 ism. The slightest variation in morphological, locomotor or biological 

 characteristics seems to be considered sufficient by many observers to 

 justify the description of a new species, and, of course, the giving of 

 a new name. Many of these names which are now retained were 

 applied prior to the epoch-making introduction of gelatin media by 

 -Koch (1881) and consequently at a time when the isolation of organisms 

 in pure culture was a matter of extreme difficulty and uncertainty. 

 One of the first facts noted by the student in taking up bacteriology is 

 the difficulty in determining motility; this property should always be 

 tested on young cultures in bouillon. In Brownian movement there 

 is a sort of scintillating movement, but the bacterium does not move 

 from that part of the field. In current movement all the bacteria 



