CH. xix.] PATHOGENIC ORGANISMS. 245 



definite disorders in the different parts. In the most 

 favourable cases (anthrax, tuberculosis), a single organism 

 introduced into a suitable locality in the animal body will be 

 capable of starting readily a new brood. But in other cases 

 it is necessary that an appreciable number of the organisms 

 be introduced in order to start a brood. This was the case 

 in some of the septicaemic processes in rodents studied by 

 Koch. 1 The period between the time of introduction of 

 the organism into the body (blood, skin, or mucous mem- 

 branes, subcutaneous tissue, lungs, alimentary canal) and 

 the production of the new brood large enough to produce a 

 definite effect locally or generally, corresponds to the 

 incubation-period of the disease, and, as is well known, 

 there is in this respect a great difference in the different 

 diseases. Thus in anthrax the introduction of the bacilli 

 into the subcutaneous tissue of a suitable animal is followed 

 after from sixteen to twenty-four hours or more by a local 

 effect (oedematous swelling), and a few hours after by general 

 constitutional illness, when bacilli can as a rule be found in 

 the blood. On the other hand, in tuberculosis after the 

 introduction of the bacilli tuberculosis into the subcutaneous 

 tissue, the nearest lymph-glands show the first signs of 

 swelling and inflammation after one week or even later, and 

 the general disease of the internal viscera does not follow 

 until one, two, or more weeks have elapsed. This is also 

 borne out by observations of the behaviour of these bacilli 

 in artificial cultures ; whereas a suitable material inoculated 

 with the bacillus anthracis and kept at the temperature of 

 the animal body (38' to 39 C.), shows already after twenty- 

 four hours a good crop of the bacilli; in the case of the 

 tubercle-bacilli the first signs of a new brood are not noticed, 

 as Koch has pointed out, and as I have had in several 

 1 Infectionskrank/teiten, loc. cit. 



