756 MODE OF SPREAD OF INFECTIVE DISEASES. 



In chicken 

 oholera. 



1880 there has been a very active movement in this 

 direction with the aim of providing an extensive appli- 

 cation of protective inoculation.* 



The starting point of this movement was Pasteur's 

 discovery that the microbes of chicken cholera could be 

 artificially attenuated, and that the inoculation of these 

 attenuated bacteria caused a local affection in fowls, after 

 recovery from which they were found to be immune 

 against inoculation with the virulent infective agents of 

 fowl cholera. On page 317 a more minute description of 

 Pasteur's experiments is given ; we need only add here 

 that two vaccines have been employed in practice, of 

 which the first is more, and the second less attenuated ; 

 the first vaccine is injected by means of a Pravaz syringe 

 at the tip of the wing of fowls, and the second 

 vaccine is employed twelve to fifteen days later. As a 

 result the animals are said to be protected against the 

 virulent bacteria. Kitt was, however, unable to confirm 

 Pasteur's results as regards the protective action of these 

 inoculations. And even if the action of the vaccine were 

 prompt, it is very seldom that it could be of practical 

 value in view of the usually very rapid spread of the 

 disease in the hen-houses which are attacked, and of the 

 length of time which must elapse till the protective in- 

 oculation is completed. The value of the inoculation is 

 also correspondingly less, because by proper disinfection 

 of the hen-houses a much more reliable prophylaxis can 

 be obtained. 



The method of protective inoculation with the artifi- 

 cially attenuated infective agents was then attempted in 

 ohe case of anthrax, symptomatic anthrax, and swine 

 In swine fever, fever. The methods employed in the two last diseases 

 have been already described on pages 300 and 307 ; it 

 was there shown that the practical value of the inocu- 

 lations against swine fever is as yet extremely doubtful, 

 while the results in symptomatic anthrax are more 



* While these pages were passing through the press a very valuable 

 paper has been published by Kitt under the title \\'ert und Unwert der 

 Schutzimpfungen gegen Thierseuchen, Berlin, 1886, to which we must 

 refer the reader for all the details with regard to protective 

 inoculations. 



In symptom- 

 atic anthrax. 



