496 BACTERIOLOGY. 
weak, and the testing for strength is still very crude, 
full doses of serum should be given if the case is at all 
serious, for the dose is limited only by the amount 
of horse-serum which we feel it safe to give, not be- 
cause we have sufficient protective substance. 
Bacteriological Diagnosis. Streptococci, using the 
name in its broadest sense, can often be demonstrated 
microscopically by simply making a smear preparation 
of the suspected material and staining with methylene- 
blue solution or diluted Ziehl’s fluid. In order to 
demonstrate them microscopically in the tissues, the 
sections are best stained by Kiuhne’s methylene-blue 
method. In all cases, even when the microscopical 
examination fails, the cocci may be found by the culture 
method on plate agar or slanted agar at 37°C. To 
obtain them from a case of erysipelas it is best, accord- 
ing to Fehleisen, to excise a small piece of skin from 
the margin of the erysipelatous area in which the cocci 
are most numerous; this is crushed up and part of it 
transfered to a gelatin tube and to the melted agar in 
another tube. After shaking thoroughly the contents 
are poured out into Petri dishes. The gelatin is kept 
at a temperature of 20° C. At the end of two or 
three days numerous small colonies develop in the 
vicinity of the particles of skin. The agar plate is 
kept at 37° C. for twenty-four hours. It is usually 
sufficient, however, to make a streak culture on agar in 
a Petri dish with the crushed excised portion of skin 
and place this in the incubator at 37° C. 
In septicemia the culture method is always required 
to demonstrate the presence of streptococci, as the micro- 
scopical examination of specimens of blood is not suffi- 
cient. For this purpose from 3 to 5 c.c. of the blood 
should be drawn from the vein of the arm aseptically 
