126 GENERAL BACTERIOLOGICAL DIAGNOSIS. 



C. Growth in bouillon, (a) character of growth, (b) 

 smell, (c) reaction. 



D. Growth on special media, (i) Solidified blood 

 serum. (2) Potatoes. (3) Lactose and other sugar media. 

 Does fermentation occur and is gas formed ? (4) Milk. 

 Is it curdled or turned sour? (5) Litmus media. Note 

 changes in colour. (6) Peptone solution. Is indol 

 formed ? 



E. What is viability of organism on artificial media ? 

 3. Results of inoculation experiments o?i animals. 



By attention to such points as these a considerable 

 knowledge is attained regarding the bacterium, which will 

 lead to its identification. In the case of many well-known 

 organisms, however, a few of the above points taken together 

 will often be sufficient for the recognition of the species, and 

 experience teaches what are the essential points as regards 

 any individual organism. In the course of the systematic 

 description of the pathogenic organisms, it will be found 

 that all the above points will be referred to, though not in 

 every case. 



The methods by which the morphological and biological character- 

 istics of any growth may be observed have already been fully described. 

 It need only be pointed out here that in giving descriptions of bacteria 

 the greatest care must be taken to state every detail of investigation. 

 Thus in any description of microscopic appearances the age of the 

 growth from which the preparation was made, the medium employed, 

 the temperature at which development took place must be noted, 

 along with the stain which was used ; and with regard to the latter it is 

 always preferable to employ one of the well-known staining combina- 

 tions, such as Loffler's methylene-blue. Especial care is necessary in 

 stating the size of a bacterium. The apparent size often shows slight 

 variations dependent on the stain used and the growth conditions of 

 the culture. Accurate measurements of bacteria can only be made by 

 preparing microphotographs of a definite magnification and measuring 

 the sizes on the negatives. From these the actual sizes can easily be 

 calculated. In describing bacterial cultures it must be borne in mind 

 that the appearances often vary with the age. It is suggested that in 

 the case of cultures grown at from 36 to 37 C. the appearances 

 between 24 and 48 hours should be made the basis of description, and 

 in the case of cultures grown between 18 and 22 C. the appearances 

 between 48 and 72 hours should be employed. The culture fluids 



