EXAMINATION OF BLOOD. 181 
are inoculated directly from the syringe, tube, or pipette 
containing the blood, the pointed end being pushed 
through the cotton-wool plug (the surface of which 
must be previously sterilised by having its projecting 
portion burnt off in the flame) and the blood allowed 
to flow drop by drop on to the surface of the 
medium, the tube being turned so that each portion 
of the medium is covered by a film of blood. If the 
tube method is used and the blood has been allowed 
to coagulate the tip of the glass tube carrying the 
needle should be broken off with a sterile pair of 
forceps or pliers. The culture tubes are then to be 
inoculated for twenty-four hours at the body tempera- 
ture and examined. If they are sterile they are to be 
returned to the incubator and examined after a further 
period. 
If colonies appear they are to be carefully examined 
with a lens, and their characters noticed. The organ- 
isms which will be most likely to develop are strep- 
tococci, staphylococci, anthrax bacilli, pneumococci, 
typhoid bacilli, the bacillus of plague, or the bacillus 
coli; the gonococcus may also develop, for it will 
obtain the hemoglobin necessary for the development 
from the blood itself. 
Streptococct form small white colonies which show no 
tendency to run together to form a film. The centre of 
each colony is more opaque than its periphery. 
Staphylococct form a more or less uniform film, the 
colonies extending laterally and fusing together. The 
growth is opaque, and is of a dead white, lemon, or 
orange colour, according to the nature of the staphylo- 
coccus present (albus, citreus, or aureus). 
Anthvax bacills form small white colonies having the 
«« barrister’s wig” appearance already described. 
