304: QUEENSLAND AGRICULTURAL JouRNAL. [1 Aprin, 1899. 
nature. In the first case it was necessary to devise a plan by which cattle 
capable of resisting the disease, but which carried the contagion constantly*in 
their blood, could be prevented from communicating this contagion; in the 
second case it is necessary to save the lives of susceptible animals which must 
be taken where they will be constantly expdsed to the contagion. 
Practical experience demonstrated many years ago that young calves are 
much less susceptible to Texas fever than mature animals, and that there was 
a minimum loss among such animals if they were taken into the infected dis- 
trict in the fall of winter. In the light of our present knowledge these facts 
mean that calves contract this disease, but suffer much less from it than do 
grown animals; that they contract the disease during the late fall, winter, or 
early spring in the infected district, and have a milder form of the disease then 
than in summer; and finally, that after recovering from this mild form of the 
disease the contagion does not as a rule affect their health. That is, in taking 
calves to the infected district in cold weather we have a method of producing 
immunity from the fever. Unfortunately this method is uncertain in its 
results and attended with heavy losses. The calves might be infected at the 
proper time or not until too late in spring; they might get a proper dose of 
the contagion, or they might be too heavily infected. 
Soon after the nature of the contagion and the part played by the ticks in 
carrying it were discovered by the Bureau of Animal Industry, experiments 
were made from which it was concluded that northern cattle might be given a 
mild attack of the disease in a number of ways. A. field might be infected by 
scattering ripe, egg-laying ticks upon it at the proper time in the fall and after- 
wards turning the cattle upon this field. By this method the time of the 
infection could be regulated, but not the extent of theinfection. In order to 
control the infection more accurately, tick-eges were collected and hatched by 
keeping them in a moderately-warm place and then placing a given number of 
young ticks upon the animals. Another method of infecting animals, shown at 
the same time to be efficacious, is to inject blood from an infected animal into 
the veins or beneath the skin of the cattle to which the mild disease is to be 
given. Itis evident that, for this purpose, there may be used either the blood 
of an immune animal from the infected district, of a sick native, or of a native 
which has been sick and recovered. By native is meant any suspectible animal 
raised in the non-infected district. 
The first systematic experiment by the bureau for the purpose of immunis- 
ing cattle was make in 1895. Eleven young animals were selected for this 
purpose, of which three were 3 months, one was 4: months, three were 5 months, 
two were 53 months, and two were 15 months old. They were inoculated b 
injecting under the skin 10 cubic centremeters, or about 24 drains, of the blood 
of cattle from the infected district. The operation was performed upon three 
in February, one in September, and seven in October. All but one of these 
- suffered more or less from mild Texas fever. One was but slightly affected, 
showing scarcely any symptons except a diminution of the red corpuscles from 
8,377,000 in a cubic millimeter of blood to 4,270,000, or about one-half the 
normal. The remaining nine were more severely affected, showing high 
temperatures ranging from 103:2 degrees to 106'5 degrees Fahr., unthriftiness, 
and emaciation. 
The great decrease in the number of red globules in a cubic millimeter of 
blood is interesting, and indicated in a general way the seriousness of the 
inoculation disease. In one the number fell from 8,297,000 to 3,640,000 ; in 
another from 8,900,000 to 2,195,000; in another from 5,470,000 to 1,502,000. 
It was from 6 to 10 weeks with the greater part before they recovered from the 
effects of the inoculation, though none appeared at any time to be in a 
dangerous condition, 
The following spring, nine of these inoculated young cattle, together with 
four animals which had been exposed to the disease and recovered after being 
slightly affected, and five which had never been exposed, were shipped to the 
infected section of Virginia and there exposed during the summer. 
, 
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