GROWTH CHARACTERISTICS 139 



are they arranged 1 (7) Does it form spores, and if so, under 

 what conditions as to temperature, etc. 1 ? 



'2. fi'roii'tk Characteristics. Here the most important points 

 on which information is to be asked are, What are the characters 

 of UTO \\th and what are the relations of growth (l)to tempera- 

 ture ; (2) to oxygen ? These can be answered from some of the 

 folloNsin- experiments : 



A. (Jrowth on gelatin. (1) Stab culture. Note, (a) rate of 

 growth ; (/>) form of growth, (a) on surface, (/?) in substance; (c) 

 presence or absence of liquefaction ; (d) colour; (e) presence or 

 absence of gas formation and of characteristic smell ; (/) relation 

 to reaction of medium. (2) Streak culture. (3) Shake culture. 

 ( \ ) Plate cultures. Note ap}>earances of colonies, (a) superficial, 

 (b) deep. (5) Growth in fluid gelatin at 37 C. 



U. (Jrowth on agar at 37 C. (1) Stab. (2) Streak. Also 

 on glycerin-agar, blood-agar, etc. Appearances of colonies in 

 airar plates. 



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

 (') reaction. 



D. Growth on social media. (1) 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 1 



K. What is the viability of organism on artificial medial 

 3. Result* <>>' inoculation experiment* on 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 hy wliicli the morphological and biological characteristics 

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

 need cnly l.r 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 tin- preparation was made, the medium employed, the temperature 

 at \\liidi 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 combinations, such as Loffler's 

 methylene-blue. Especial care is necessary in stating the size of a 



