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 Zeitschrift fiir Thiermedicin (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- 
ying 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 thesame 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 
