PROTECTIVE INOCULATIONS. 291 



fowls are insusceptible to inoculation with the strongest virus. And this, 

 without any sickness, or even local necroses, which Pasteur describes as fol- 

 lowing vaccinations with his attenuated virus." 



In discussing the practical value of this method Salmon estimates 

 the cost as trifling " not more than half a day's time of one man for 

 one hundred fowls, even if three inoculations were made." 



In a paper on protective inoculations against fowl cholera, by Kitt, 

 in the Deutsche Zeitsclirlft fur Tltiermedicm (December 20th, 1886), the 

 conclusion is reached that these inoculations undoubtedly protect the 

 fowls from infection either in the natural way or by inoculations with 

 virulent material. But Kitt doubts the practical utility of the method 

 for the arrest of epidemics of this disease in the poultry yard; and, 

 as we think with justice, prefers to depend upon cleanliness, disin- 

 fection, and prompt removal of infected fowls. As he points out, a 

 considerable time is required to produce complete immunity, and two 

 inoculations are often insufficient. Pasteur had previously reported 

 that a third inoculation is usually required. But the infection 

 spreads so rapidly when an epidemic is developed in a poultry yard 

 that a large proportion of the fowls would be likely to perish before 

 the protective inoculations could be carried out. Another objection 

 is that when inoculated in the breast muscle the value of the fowl for 

 the table is reduced, and when inoculated in the wing an unpleasant- 

 looking scab is left at the point of inoculation. The cost in material 

 and time required to carry out the three successive inoculations is 

 also an objection to the practical application of the method. More- 

 over, the excreta of the inoculated fowls contain the pathogenic mi- 

 crobe, and it would evidently be unwise to practise inoculations in 

 poultry yards not already infected. Kitt states also that he has 

 always succeeded in stamping out the disease very promptly by the 

 other measures referred to disinfection, cleanliness, separation of 

 all fowls which show any indications of being infected. 



In a more recent paper (1893) Kitt reports his success in confer- 

 ring immunity upon fowls by a new method, which is, however, 

 rather of scientific interest than of practical value. He first experi- 

 mented to see whether the blood serum or tissue juices of immune 

 fowls would give immunity against cholera to other fowls, and ob- 

 tained a successful result. He was not, however, able to produce im- 

 munity in pigeons or in rabbits by the same method. He next under- 

 took to determine whether the immunizing substance was present in 

 the eggs of fowls which had an immunity as a result of protective in- 

 oculations. The albumen and yolk of the egg, in doses of five to ten 

 cubic centimetres, was injected into the breast of fowls, and at the end 



