556 MICRO-ORGANISMS AND DISEASE [chap. 



cavity from the interior of the intestine is the only one that 

 can be admitted. Now this peritoneal accidental bacillus 

 coli after cultivation proves highly virulent for the guinea-pig, 

 a small dose injected subcutaneously produces acute 

 haemorrhagic septicaemia easily transmissible from guinea- 

 pig to guinea-pig. 



Bacillus anthracis of one source or another possesses 

 different degrees of virulence (as has been mentioned in the 

 chapter on Anthrax), thus if a comparatively large dose of 

 anthrax bacilli in the blood of a mouse be injected into a sheep 

 perhaps only transitory illness will be the result, the sheep' 

 possessing a certain amount of resistance against the mouse- 

 bacilli, but if a few drops of blood of sheep dead of anthrax 

 be used for subcutaneous injection of a normal sheep fatal 

 anthrax will be the result. 



(d) That the amount, i.e. the number, of the microbes 

 introduced plays an important part has been mentioned on 

 various previous occasions ; here are a few more examples : 

 A guinea-pig is susceptible to virulent anthrax if only a 

 few bacilli are injected subcutaneously (Watson Cheyne, 

 Lubarsch), while for the rabbit to achieve this result a con- 

 siderably greater number is required, and in the case of a 

 dog not even large doses suffice to produce infection. 



The bacillus of fowl cholera taken from a drop of the 

 blood of a fowl dead of the disease, injected subcutaneously 

 into a rabbit or a pigeon, produces acute fatal infection, in 

 the guinea-pig such a dose produces no result. A small 

 particle of a glanders nodule of the horse injected subcu- 

 taneously into a guinea-pig or a field mouse produces fatal 

 infection, in a rabbit it produces local abscess, and in a 

 normal white mouse produces no result or only a slight 

 transitory tumour. 



These, as stated above, are only a few examples amongst 



