BIOLOGICAL PROPERTIES 477 



insignificant. The best medium for cultivation is 5 per cent, glycerin- 

 agar but even under the most favourable conditions growth is always scanty. 



Broth. Cultivation of the micrococcus in broth gives rise, after incubating 

 for three days at 37 C., to an uniform cloudiness in the medium without any 

 surface pellicle. 



Agar. Stab culture. Small spherical colonies develop along the line of 

 sowing and these may ultimately unite together to form a yellowish streak 

 with denticulated edges. 



Stroke culture. Very small transparent colonies measuring 2-3 mm. in 

 diameter are visible about the third day : on further incubation they become 

 raised, smooth, shiny ana milky-white in appearance. 



On glycerin-agar and glucose-nutrose-agar the growth is more rapid and 

 more abundant. 



Gelatin. At 22 C. the amount of growth is nil or insignificant. The 

 medium is not liquefied. 



Potato. No apparent growth takes place on potato. 



Milk. The reaction becomes alkaline. The milk is not coagulated. 



SECTION in. BIOLOGICAL PROPERTIES. 

 1. Vitality. 



Cultures of the micrococcus will keep alive for a long time in the laboratory ; 

 Shaw was able to obtain sub-cultures from a broth culture 5 months old and 

 also from a nine -months old growth on a dried-up tube of agar. 



In sterilized earth the organism lives at least 69 days (Horrocks) and in 

 cloth eighty days. In water and in moist soil it does not seem to live so long : 

 Horrocks could not recover the organism from sterile water after a week but 

 Shaw in a similar experiment recovered it after 50 days. 



Cultures can be sterilized by heating them at 60 or 65 C. for half an hour. 



2. Bio-chemical reactions. 



The Micrococcus melitensis does not ferment sugars and produces no 

 indol. 



3. Toxin. 



The toxin of the Micrococcus melitensis was studied by Shaw. 



In monkeys the inoculation of porcelain-filtered broth cultures only pro- 

 duces a negligible reaction. The blood of the inoculated monkeys exhibits 

 feeble agglutinating properties (1 in 80). 



Inoculation of cultures heated to 60 or 70 C. for half an hour produces 

 hardly any more reaction, but the serum of the inoculated animal has more 

 marked agglutinating properties (up to 1 in 500). 



4. Immunity. Vaccination. 



Bruce has shown that an attack of Mediterranean fever renders the patient 

 immune to subsequent infection, but that the immunity is not absolute. 

 In monkeys which had recovered from one attack of the experimentally induced 

 disease, a second mild attack unaccompanied by bacillsemia was produced 

 by inoculating them a second time (Shaw). 



Animals easily resist the inoculation of large quantities of killed cultures, 

 but this does not produce any immunity against the living organism, since 

 the subsequent inoculation of a small dose of a living culture almost certainly 

 kills them (Eyre). Shaw, however, after giving monkeys several sub- 



