386 THE ALCALIGENES— DYSENTERY— TYPHOID GROUP 
Immmiity and Immunization to Paratyphoid Infection.— The dura- 
tion of immunity following recovery from an attack of paratyphoid 
fever or of meat poisoning is as yet undetermined. The brilHant 
results of protective immunization against typhoid fever with vaccines 
or residues of the typhoid bacillus have led to similar vaccination 
against paratyphoid infection with polyvalent vaccines composed of 
the principal strains of the paratyphoid group. Combined protective 
vaccination against typhoid and paratyphoid by the use of compound 
vaccines has also been attempted. The efficiency of the immunization 
appears to have been proven by the success of the wholesale immuniza- 
tion of large military groups by the triple typhoid-paratyphoid alpha- 
beta vaccine. (T-A-B-vaccine.) 
Dissemination and Prophylaxis.— Farsityphoid fever appears to be 
spread by mild unrecognized cases, by carriers, and by the occasional 
transmission of bacilli through food, water or milk. Flies may also 
be a factor in the dissemination of the organisms. Meat poisoning 
is chiefly disseminated by infected meats, more frequently that of 
cattle or swine. The customary precautions appropriate for excremen- 
titious diseases, including the restriction of carriers, may be con- 
fidently relied upon to prevent the spread of paratyphoid fever. 
Thorough cooking will largely reduce the occasional danger from 
contaminated meats. 
MORGAN BACILLUS. 
Morgan^ has isolated a bacillus, apparently intermediate in its 
general chemical and pathological characteristics between the para- 
typhoid andtheproteus groups, from a series of diarrheal cases of greater 
or lesser severity. The organism measures approximately 2 microns 
in length, and 1 micron in diameter. It is motile, and possesses peri- 
trichic flagella. Spores and capsules have not been demonstrated. It 
stains readily with ordinary anilin dyes, but fails to retain the Gram 
stain. 
Isolation and Culture.— The organism grows luxuriantly upon ordi- 
nary cultural media, and colonies are readily obtained upon agar or 
gelatin plates. The colonies, even after eighteen hours' incubation 
at 37° C, are about 2 mm. in diameter, round, clear, and slightly 
raised in the center. Neither gelatin, casein nor blood serum are 
liquefied. 
x'Ycid and gas are produced in glucose, but not in lactose, saccharose • 
or mannitol. Indol is produced in considerable amount in plain 
nutrient bouillon. 
A slight initial acidity, rapidly followed by a progressively alkaline 
reaction, is produced in milk, but the casein is not precipitated. The 
organism is facultatively anaerobic, growing best at 37° C. Growth 
ceases below 8° C. and above 43° C. 
1 British Med. Jour., 1906, i, 908. 
