140 ORIENTAL PLAGUE chap. 



inoculation does not extend into the subcutaneous tissue 

 — the guinea-pig, as mentioned already, develops the sub- 

 acute form of plague. Only in very rare instances, i.e. in 

 cases of exceptionally virulent material, have I seen acute 

 plague in the guinea-pig after cutaneous inoculation, that 

 is plague showing the symptoms of the acute form, death 

 ensuing in or about seventy -two hours. Amongst the 

 many dozens of guinea-pigs, which I have had occasion to 

 experiment on during the last half-dozen years, I have 

 only once dealt with material of such virulence that the 

 two guinea-pigs inoculated cutaneously with it developed 

 the acute and not the subacute form. I have had, 

 however, on several occasions, guinea-pigs which died in 

 four days, and which showed something of a transition 

 between acute and subacute plague — that is, it showed 

 the appearances of the bubo and of the spleen which to 

 the unaided eye were those of acute plague as described 

 above, but on more minute examination in the inguinal 

 lymph gland of the bubo there was nevertheless found one 

 or the other necrotic focus, and the spleen also contained 

 a few minute white punctiform nodules. The sub- 

 cutaneous injection of the guinea-pig is in my experience 

 an excellent test for deciding whether a given material 

 is of normal or subnormal virulence, and whether the 

 B. pestis of it corresponds to type 1 (man) or type 2 (rat) ; 

 for if the material injected in small dose causes the acute 

 form of plague it may be accepted to be of the normal, if 

 it causes the subacute form it may be considered of the 

 subnormal virulence. But the cutaneous inoculation of 

 the guinea-pig is not of this diagnostic value, since, except 

 in the few rare cases mentioned, the guinea-pig responds 

 to this form of inoculation with the subacute form of 



