THE PNEUMOCOCCUS 327 
may be used. The portion of mucus, washed as for mouse inocula- 
tion, is introduced into a sterile centrifujje tube containing 1 per 
cent of ghicose broth reinforced with 5 per cent of sterile, defibrinated 
rabbit blood. Inoculation is practised at 37° C. for five hours, ^ or 
until a fairly luxuriant growth is obtained. A Gram stain will deter- 
mine both the relative purity of the culture and the degree of pro- 
liferation of the pneumococci. 
If the growth is fairly pure, the agglutination test is set up precisely 
as for the culture from the mouse. 
If considerable numbers of pneumococci are present but associated 
with other bacteria, 1 cc. of sterile ox-bile is added, and incubated 
for one-half hour to dissolve the pneumococci. The culture is centric 
fuged until a water-clear supernatant fluid is obtained, which is tested 
for specific pneumococcus precipitins, using type sera as above indi- 
cated. 
Blake- has noticed that a specific precipitin reaction may frequently 
be obtained by adding the water-clear supernatant fluid from the 
peritoneal washings of the mouse (centrifuged at high speed) in 
amounts of 0.5 cc. to an equal volume of the respective sera, as follows: 
■itoneal washings, 
Water-clear. 
Specific serums 
(0.5 cc). 
0.5 CC. 
Tjiie I 1:10 
0.5 " 
" II 1:10 
0.5 " 
" III 1:50 
The homologous serum gives a precipitate which forms very quickly. 
Incubation is frequently unnecessary. The urine frequently contains 
a soluble substance which gives a positive precipitation reaction. One- 
half a cubic centimeter of urine is added to each of the undiluted type 
sera (0.5 cc.) and examined at once, and after one hour for a precipita- 
tion reaction in the homologous serum. 
Pneumococci isolated from pleural and pericardial exudates, middle- 
ear infection, empyema and pneumococcic cerebrospinal meningitis 
can be identified morphologically by their lanceolate shape and Gram- 
positiveness; the type of organism, however, must be determined by 
serological reactions. 
They are best obtained in pure culture, if they are mixed with other 
bacteria, upon blood agar plates. A green halo surrounds the typical 
pneumococcus colony. 
The prophylaxis is the same as for any acute respiratory disease. 
1 It is advantageous to warm the medium to 37° C. prior to iiiopulatinn. An hour or 
more is saved in the period of incubation by this procedure. 
2 Jour. Exp. Med., 1917, 26, 67. 
