DESCRIPTION OF PLATES. xxiii 



FIG. 3. On the surface of Nutrient Agar-agar. Pure-cultivation of Bacillus 

 indicus on the surface of obliquely solidified nutrient agar-agar. The 

 growth has the colour of red sealing-wax, and a peculiar crinkled 

 appearance. After some days it loses its bright colour and becomes 

 purplish, like an old cultivation of Micrococcus prodigiosus. 



FIG. 4. On the surface of Nutrient Agar-agar. A pure-cultivation obtained 

 from an abscess (Staphylococcus pyogenes aureus). 



FIG. 5. On the surface of Nutrient Agar-agar. A pure-cultivation obtained 

 from green pus (Bacillus pyocyaneus). The growth forms a whitish, 

 transparent layer, composed of slender bacilli, and the green pigment 

 is diffused throughout the nutrient jelly. The growth appears green by 

 transmitted light, owing to the colour of the jelly behind it. 



FIG. (\.-On tlie surface of Potato. A pure-cultivation of the bacillus of 

 glanders on the surface of sterilised potato. 



DESCRIPTION OF PLATE III. 



Plate-cultivation. 



Following p. 108. 



This represents the appearance of a plate-cultivation of the comma-bacillus 

 of Cholera nostras, when it is examined over a slab of blackened plate-glass. 

 The drawing was made from a typical result of thinning out the colonies by 

 the process of plate-cultivation. At this stage they were completely isolated 

 one from the other ; but later they became confluent, and produced complete 

 liquefaction of the gelatine. 



DESCRIPTION OF PLATE IV. 



Streptococcus Pyogenes. 



Following p. 178. 



FIG. 1. From a cover-glass preparation of pus from a pyaemic abscess. 

 Stained with gentian-violet by the method of Gram, and contrast-stained 

 with eosin. x 1200. Powell and Lealand's apochromatic T \ Horn. imm. 

 E. P. 10. 



FIG. 2. From cover-glass preparations of artificial cultivations of the strepto- 

 coccus in broth and in milk at different stages of growth, x 1200. Powell 

 and Lealand's apocbromatic -fa Horn. imm. E. P. 10. 



In these preparations there is a great diversity in size and form of the 

 chains and their component elements. In the drawing examples are 

 figured of the following: 



(a) Branched chains. 



(b) Simple chains composed of elements much smaller than the 

 average size. 



O) Chains with spherical and spindle-shaped elements at irregular 



intervals. These are conspicuous by their size, and are sometimes 



terminal. 



(d e) Chains in which the elements are more or less uniform in size. 

 (/) Complex chains with elements dividing both longitudinally and 



transversely, and varying considerably in size in different lengths 



of the same chain. 



