IXODIC ANEMIA — TEXAS FEVER, ETC. 421 



' Had there been a well-marked immunity conferred by in- 

 oculation, it would have been possible to have improved the 

 method of procedure; and perhaps carefully prepared blood 

 serum, freed from the organism, might have been of great value. 

 One remarkable instance is mentioned in the report, namely, 

 that the Texas fever parasite was found in the blood of a North 

 Carolina animal three years after it had left the permanent 

 infected territory. 



Similar diseases, manifested by coloured urine, are reported to 

 prevail in the marshy regions of Eoumania. These were investi- 

 gated by Babes in 1888, and disseminated largely by draught oxen: 

 in the Cape of Good Hope also conveyed from place to place by 

 yoke oxen. By keeping communication with the territory north 

 of the colony, these cattle, like those of the Southern States, 

 seem not to infect others directly, but they infect ground 

 over which they have passed. It also prevails in Australia, and 

 is due to the same cause, ticks being numerous in that country. 

 Infected pastures have been found to be harmless to sheep, 

 and it is thought that other domesticated animals may graze 

 unharmed in such pasture. 



The discovery that the disease is conveyed by ticks explains 

 what has hitherto been very mysterious, namely, that Northern 

 cattle become affected by the disease when pastured on lands 

 previously grazed by Southern cattle apparently in perfect 

 health. This fact leads to the conclusion that Southern cattle, 

 recovered, perhaps, from previous attacks, have acquired im- 

 munity, though covered with ticks. 



Although it is clearly demonstrated that Southern cattle are 

 dangerous when they bear the cattle tick, and that this tick 

 conveys the micro-parasite from Southern to healthy Northern 

 cattle ; but transmission from Northern cattle is very rare. 



Northern cattle have ticks on them, but only those which 

 survive the disease or die after a prolonged attack ripen the 

 tick on their bodies. Those which die of an acute attack in 

 a short time after infection have only immature ticks on them. 

 If the fever has occurred early enough in the season to permit 

 a second generation of ticks to appear before the cold weather 

 arrives, another outbreak during the same season may occur. 

 Usually the first outbreak occurs in August, and the second, to 

 be looked for late in September or early in October, is so mild 

 as to pass unobserved. If, however, the first outbreak occur 



