THE PARATYPHOID GROUP 3S3 
efficiency of refrigeration of meats in the warmer months. The incu- 
bation period may be as brief as four to six hours, or as long as twenty- 
four to seventy-two hours after ingestion of the infected food. The 
initial symptoms are usually a severe headache and chill, rapidly 
followed by acute gastro-intestinal disturbances, dizziness, nausea 
and vomiting, abdominal pain and diarrhea. Nervous symptoms and 
marked restlessness are characteristic of the severe and fatal cases. 
Usually the symptoms and fever abate within a week; they may 
persist for several weeks. The mortality is, as a rule, low, averaging 
from 1 to 2 per cent. The conspicuous lesion observed at autopsy 
is an intense hyperemia of the gastro-intestinal mucosa, usually with- 
out noteworthy involvement of Peyer's patches. Fatty degeneration 
of the liver is common. Bacilli (usually B. enteritidis or B. cholera^ 
suis,^ less commonly B. paratyphosus beta) may be isolated from the 
feces and blood stream in many of the acute cases during the first 
few days of the disease. They are almost invariably recovered from 
the heart blood and spleen at autopsy. Serum reactions, especially 
specific agglutinins, may be demonstrated at the end of the first week 
in many but not all cases. 
An epidemic of meat poisoning is characterized by the sudden, 
practically simultaneous onset of symptoms in those who have eaten 
the contaminated food, and the limitation of the disease to the primary 
cases. Secondary infection is uncommon. It should be remembered 
that not all epidemics of meat poisoning are caused by members of 
the paratyphoid group of bacteria. 
Distribution of Organisms.— The hog cholera bacillus (B. cholerse 
suis, B. suipestifer) is frequently found in the intestinal tracts of 
swine, rats and mice; probably somewhat less commonly in cattle. 
B. enteritidis is a frequent inhabitant of the intestinal contents of 
rats and mice, and relatively uncommon in healthy cattle.- It is 
suspected that a postmortem infection of beef is more common than 
an antemortem invasion; this is reasonably suggested by the wide 
distribution of rats and mice in slaughter houses. The bacteria 
possess the somewhat unusual property of rapidly diffusing themselves 
through the substance of meat after they have been distributed on 
the surface of it by careless handling. Unless infected meat is thor- 
oughly cooked, the organisms are not killed, and they may not l)e 
even weakened if the degree of heat and time of exposure is insuffi- 
cient. The endotoxins of the bacilli, furthermore, are relatively 
thermostabile. Thorough cooking of such meat is essential to insure 
safety. 
(6) Paratyphoid Fe?;er.— Bacteriologically, paratyphoid fever may 
be caused either by B. paratyphosus alpha or B. paratyphosus beta. 
Clinically there is little or no difference between the two infections. 
According to Bainbridge,-^ paratyphoid fever in Asia, particularly in 
1 Bainbridge: Lancet, 1912, i, 705, 771, 849. 
2 Bainbridge: Loc. cit. » Lancet, 1912, i, 705, 771, 849. 
