300 
Tick Paralysis 
Experiment I. (Negative.) 
26. vn. 1912 Z). venustus larvae were placed on a guinea-pig. 
29. VII. -1. VIII. 12 Larvae dropped off gorged. 
8 . VIII. 12 Nymphs began to emerge. 
13. IX. 12 Nymphs placed on a guinea-pig. 
18-23. IX. 12 Nymphs dropped oS gorged. 
2. X. 12 Adults emerged. 
24. XI. 12 Adults (4 J s, 4 ? s) placed on ram’s scrotum. 
9. XII. 12 1 $ dropped off gorged. 
Experiment II. 
6. VIII. 1912 
9-12. VIII. 12 
20 . viii. 12 
19. X. 12 
24. X. 12 
Experiment III. 
7. IV. 1913 
9-10. IV. 13 
11. IV. 13 
17. IV. 13 
( 13. V. 13 
dt 'j 
1 19. V. 13 
t 2. VI. 13 
b. 8-13. VI. 13 
V 23. VI. 13 
10. VII. 13 
18. VII. 13 
D. venmtus larvae were placed on a guinea-pig. 
Larvae dropped off gorged. 
Nymphs began to emerge. 
Nymphs placed on a guinea-pig. 
Guinea-pig died on the 6th day after the nymphs were applied. 
D. venustus larvae were placed on a guinea-pig. 
Larvae dropped off gorged. 
Guinea-pig died on .5th day after the ticks were applied. 
Nymphs began to emerge. 
Nymphs placed on a guinea-pig. 
Guinea-pig died on 7th day after ticks were applied. 
Nymphs placed on a ram’s scrotum. 
Nymphs dropped off gorged. 
Adults began to emerge. 
Adults (3 ? s, 3 j s) placed on ram’s scrotum. 
1 ? dropped off gorged. 
Conclusions. 
The condition of “ Tick Paralysis ” experimentally produced in a dog 
in Cambridge through the application a single Bermacentor venustus $ 
from Canada is the same as that observed in sheep, as described in the 
preceding paper. The examination of the dog’s blood proved negative. 
The negative results of inoculations and the absence of fever indicate 
that the disease is not infective, although the incubation period suggests 
the contrary. On the hypothesis that the symptoms are due to toxins 
given oflf by the tick, the “ period of incubation ” might be explained on 
the supposition that it is only when the tick commences to engorge or 
feed rapidly, some days after it has become attached, that it gives off 
the hypothetical toxin in its saliva in sufficient quantity to produce 
pathogenic effects. Where the ticks are picked or rubbed off early no 
