286 
Tick Paralysis 
pi'obable. Nuttall (1908) mentions the fact that the bites of the 
nymphs of Ornithodoriis rnouhata are more to be feared for their after¬ 
effects than the bites of the adults, quite apart from the transmission of 
the disease. 
In referring to the paragraph on the history of the disease, it will 
be seen that the old sheep became paralysed the first year and that 
only yearlings were attacked in subsequent years, showing that an 
immunity is produced after one attack. This does not interfere with 
the toxin hypothesis, for examples of immunity following the repeated 
bites of other arthropods (mosquitoes, etc.) are common. Rocky 
Mountain fever is the only other disease known to be transmitted by 
D. venustus, and at first it seemed possible that there might be some 
connection between the two diseases, but so far there seems to be no 
evidence of the occurrence of Rocky Mountain fever in British 
Columbia. 
The symptoms of “ tick paralysis ” in lambs develop gradually. 
The first noticeable sign is restlessness, the lambs at times stagger 
about and bump against obstacles and occasionally fall when trying to 
stop ; later on they fall down and cannot rise ; at this stage they struggle 
a great deal. As paralysis advances the lambs cease struggling but still 
have a wild-eyed look; they drink milk with less avidity. As soon as 
recovery begins they again continually siruggle in their attempts to 
rise, and this continues until they are able to stand, after which recovery 
is very rapid. 
No efforts have as yet been made to treat the affected animals, but 
this will be undertaken in the course of further investigations. It 
would appear advisable, however, on general principles, to remove the 
ticks from affected animals and to resort to dipping, if possible. 
The local effects of the bites of D. venustus. 
The ticks are easily found on newly shorn sheep, because soon after 
a tick becomes attached it voids excrement which collects and dries in 
the hair, thus forming a dark reddish patch. Male ticks frequently 
attach and detach themselves, and whenever they do so bleeding is pro¬ 
fuse ; the blood seetns to have lost its clotting properties. In PI. XXI, 
fig. 1, the effects of the bites under a lamb’s skin are visible. The 
liaemorrhages have some resemblance to those seen in cases of haemo¬ 
philia. In man, shortly after being bitten, a scarlet, irritable patch 
appears. I was once bitten on the neck by a male. The bite was not 
