Diagnosis 555 



peritoneal exudate rich in leukocytes and containing characteristic 

 chains of the plague bacillus, occurring in from twenty-four to 

 forty-eight hours. 



Diagnosis. — It seenas possible to make a diagnosis of the disease 

 in doubtful cases by examining the blood, but it is admitted that a 

 good deal of bacteriologic practice is necessary for the purpose. 



Abel found that blood-examinations may yield doubtful results 

 because of the variable appearance of the contained bacilli, which 

 may easily be mistaken for other bacteria. He deems the best 

 tests to be the inoculation of broth cultures and the subsequent 

 inoculation into animals, which, he advises, should have been pre- 

 viously vaccinated against the streptococcus. 



KoUe* has suggested a method valuable both for the diagnosis 

 of the disease and for estimating the virulence of the bacillus. It 

 is as follows: "The skin over a portion of the abdominal wall of 

 the guinea-pig is shaved, care being taken to avoid the slightest 

 injury of the skin. The infective material is carefully rubbed into 

 the shaved skin. Important, in order rightly to understand the 

 occurrence of plague infection, is the fact disclosed here in the case 

 of guinea-pigs, that by this method of inoculation the animals 

 present the picture of true bubonic plague — that is to say, the pro- 

 duction of nodules in the various organs, principally in the spleen. 

 In this manner guinea-pigs, which would not be affected by large 

 subcutaneous injections, even amounting to 2 mg. of agar culture 

 (equal to a loop) of low-virulence plague bacillus, may be infected 

 and eventually succumb." 



The postmortem appearance of the body of a plague-infected 

 rat is as follows if Subcutaneous hemorrhages occur in about 40 

 per cent, of the animals and are most frequently to be seen in the 

 submaxillary region. Buboes are present in the majority of cases, 

 usually in some one locality, and commonly about the neck. The 

 liver may show necrotic changes which have the appearance of an 

 excessive deposit of fat, and a condition of the greatest importance 

 in diagnosis is the occurrence of small necrotic foci scattered over 

 its surface and throughout its substance. The spleen is firm and 

 does not collapse like a soft normal spleen; granules or nodules may 

 be well marked in it and may be confluent. The kidneys and 

 suprarenal capsules are often congested. Hemorrhages are fairly 

 common in the lungs and visceral pleura. The presence of pleural 

 effusion is very characteristic and of great value in diagnosis. In 

 naturally infected plague rats, tfie most important features for 

 purposes of diagnosis are: 



I. A typical bubo — most commonly in the neck. 

 . 2. Granular liver — not seen except in plague rats. 



* "See Havelburg, "Public Health Reports," Aug. 15, 1902, vol. xvil. No. 33, 



t See "Journal of Hygiene," 1907, vii, 324. 



