584 



THE PNEUMOCOCCUS 



Friedlander's method. 1. Stain the section in the following solution for 

 24 hours : 



Fuchsin, - 1 gram. 



Absolute alcohol, 5 grams. 



Glacial acetic acid, - 2 ,, 



Distilled water, - 100 



2. Wash in alcohol and then in 2 per cent, acetic acid for 2 minutes. 



3. Wash in distilled water, dehydrate in absolute alcohol, clear in clove 

 oil or xylol and mount in balsam. 



Ribbert's method. 1. Stain the section for a few minutes in the following 

 solution : 



Distilled water, - 

 95 per cent, alcohol, 

 Glacial acetic acid, 

 Violet-dahlia, 



grams. 



2. 



- 100 

 50 

 12*5 



Q.8. to saturate 

 in the warm. 



Wash in water, dehydrate in absolute alcohol, clear in clove oil or xylol. 



and mount in balsam. 



B. Appearance in cultures. In cultures on artificial media generally the 

 pneumococcus is not encapsulated ; capsules are only found in cultures in 

 liquid serum or blood-broth. 



In cultures, the pneumococcus appears either as lancet-shaped cocci, or as 

 rounded grains : the latter may be found to the absolute exclusion of the 

 lanceolate forms. The organism may occur as single cocci, as diplococci, 

 or in short streptococcal chains of 3 to 8 elements : the chains consist of 

 chains of diplococci, the long axes of the cocci being dis- 

 posed along the line of the chains. The latter are especially 

 numerous and long in broth cultures. 



2. Cultural characteristics. 



Conditions of growth. The pneumococcus is a facultative 

 aerobe. Growth does not take place below 25 C. so that 

 the organism cannot be cultivated on ordinary gelatin. The 

 optimum temperature is about 35-37 C.. and development 

 ceases at 42 C. Growth is more vigorous in liquid than on 

 solid media, and the medium must be faintly alkaline : 

 ordinary media are not very suitable for cultivating the 

 pneumococcus. 



Agar. After incubating for 24 hours at 37 C 

 growth of small transparent colonies resemblin 

 dew is seen. The colonies are difficult to see am 

 confluent. 



Coagulated serum. The growth is similar to that on agar, 

 but differs from the latter in that the colonies occasionally 

 coalesce and form a thin semi-transparent film. 



Burger's serum (p. 590). 



Broth. After incubating at 37 C. for 24 or 36 hours the 

 medium is very slightly cloudy : a very delicate powdery 

 deposit is precipitated later. Broth containing 8 per cent. 

 glucose is a much better medium than ordinary broth 

 (Turro). 



Broth containing rabbit's blood. To prepare this medium a little blood is 

 collected aseptically from the ear vein of the rabbit (p. 194) and added to 

 sterilized broth in the proportion of 1 part of blood to 3 or 4 parts o 



a delicate 

 drops of 

 are never 



FIG. 277. Pneu- 

 mococcus. Surface 

 culture on agar (3 

 days at 37 C.). 



