EXPERIMENTAL INOCULATION 431 



in the secondary lesions mentioned they are often abundant. 

 In the pulmonary form the lesion is the well-recognised " plague 

 pneumonia." This is of broncho-pneumonic type, though large 

 areas may be formed by confluence of the consolidated patches, 

 and the inflammatory process is attended usually by much 

 haemorrhage ; the bronchial glands show inflammatory swelling. 

 Clinically there is usually a fairly abundant frothy sputum often 

 tinted with blood, and in it the bacilli may be found in large 

 numbers. Sometimes, however, cough and expectoration may 

 be absent. The disease in this form is said to be invariably 

 fatal. In the septiccemic form proper there is no primary bubo 

 discoverable, though there is almost always general enlargement 

 of lymphatic glands ; here also the disease is of specially grave 

 character. A bubonic case may, however, terminate with septi- 

 caemia ; in fact all intermediate forms occur. An intestinal form 

 with extensive affection of the mesenteric glands has been 

 described, but it is exceedingly rare so much so that many 

 observers with extensive experience have doubted its occurrence. 

 In the various forms of the disease the bacilli occur also in the 

 blood, in which they may be found during life by microscopic 

 examination, chiefly, however, just before death in very severe 

 and rapidly fatal cases. The examination of the blood by means 

 of cultivation experiments is, however, a much more reliable 

 procedure. For this purpose about 1 c.c. of blood may be with- 

 drawn from a vein and distributed in flasks of bouillon (p. 68). 

 It may be said from the results of different investigators that 

 the bacillus may be obtained by culture in fully 50 per cent of 

 the cases, though the number will necessarily vary in different 

 epidemics. The Advisory Committee, recently appointed, found 

 that in some septicaemic cases the bacilli may be present in the 

 blood in large numbers two, or even three, days before death, 

 though this is exceptional. 



The above types of the disease are usually classified together 

 under the heading pestis major, but there also occur mild forms 

 to which the term pestis minor is applied. In these latter there 

 may be a moderate degree of swelling of a group of glands, 

 attended with some pyrexia and general malaise, or there may 

 be little more than slight discomfort. Between such and the 

 graver types, cases of all degrees of severity are met with. 



Experimental Inoculation. Mice, guinea-pigs, rats, and 

 rabbits are susceptible to inoculation, the two former being on 

 the whole most suitable for experimental purposes. After sub- 

 cutaneous injection there occurs a local inflammatory cedema, 

 which is followed by inflammatory swelling of the corresponding 



