BACILLUS M ELI TEN SIS 419 
gelatin, without producing liquefaction, and it produces a slight 
turbidity in broth. Milk appears to be a good medium for its develop- 
ment, goats' milk being somewhat better than cows' milk for this 
purpose. 
The organism is aerobic, facultatively anaerobic. The minimum 
temperature of growth is about 8° C, the optimum 37° C, and the 
maximum about 44° C. Direct sunlight kills it in a few hours; an 
exposure to 55° C. is usually fatal within an hour; 1 per cent carbolic 
acid kills it in ten to fifteen minutes.^ It resists drying in the cold and 
in the dark for several weeks. 
Products of Growth. — B. melitensis is culturally inert;- it produces no 
proteolytic enzymes and it produces neither acid nor gas in any sugars. 
Milk, particularly goats' milk, becomes progressively alkaline in 
reaction. Soluble toxins have not been demonstrated. Besredka'' 
has separated a poisonous substance of the nature of an endotoxin from 
the substance of the organism. 
Gelatin is not liquefied and indol or other decomposition products 
of the aromatic amino-acids have not been found in cuhures. 
Pathogenesis. — .4??i7/ia/.— Apes are susceptible to inoculation with 
B. melitensis; the subcutaneous inoculation of cultures of the organism 
leads to definite clinical symptoms parallel to those observed in man. 
The disease usually runs a prolonged course and is often fatal. IVIonkeys 
are somewhat less favorable subjects than apes. Goats, sheep, cattle* 
and horses are also susceptible to infection, although the disease is 
rarely generalized. The presence of the virus in the urine of the males, 
and in the milk and urine of the females of these species is the principal 
indication of infection. The incubation period is from five to fourteen 
days. Eyre' states that rabbits and guinea-pigs may be infected, but 
not rats and mice. 
Milk appears to be the chief source of infection. On the Island of 
Malta, where ^lalta fever was first described, fully 10 per cent of 
the female goats contained the organism in their milk. Butter and 
cheese made from infected milk contained B. melitensis. Monkeys 
readily contract the disease by drinking this milk. The urine of both 
male and female goats was shown to be infected as well. 
Immunity and Immunization.— The blood and urine of infected indi- 
viduals contain the virus of the disease and the organism is readily 
isolated from the urine of patients. Specific agglutinins are present 
in the blood, even early in the disease. The agglutinins may persist 
for years after convalescence. Dilutions of yio" to t¥¥¥¥ ^^e made 
from the blood serum with suitable controls.*' A small amount of 
1 Mohler and Eichhorn: Bureau of Animal Industry, 1911, 28, 125. 
2 Kendall, Day and Walker: Jour. Am. Chem. Soc, 1913, 35, 1247. 
3 Bull. Inst. Pasteur, 1914, 12, 193. 
4 Evans: Public Health Reports, 1923, 38, 825. 
^ KoUe and Wassermann: Handb. d. Path. Mikroorganismen, I. Erganzband. 
^ It has been claimed that Bacillus abortus and Bacil'us melitensis possess agglu- 
tinins in common, 
