310 A TIfK-BESISTANT CONDITION IN CATTLE. 



<3alved on 15th Angtist, 1918 ; Queenie on 6th October, 

 1917 ; Pocahontas on 29th April, 1918 ; Frida on 18th July. 



The condition just described appears to graduate into 

 a type of tick-sore, so far only noticed on resistant animals. 

 The scab formed over such a tick sore consists of two very 

 distinct parts — -an outer ring of a clear yellow substance, 

 apparently composed of exactly the same matter as that 

 spoken of above, surrounding a dark blood-stained core, 

 -on the upper surface of which there is a pit, where the mouth 

 parts of a tick have been inserted* ; very often the tick is 

 still present. Development up to the adult stage occurs 

 in such ticks but the females are unable to bloat and remain 

 stunted, sickly-looking individuals, eventually dropping off 

 with the scab. The under surface of this hard black core, 

 surrounding the rostrum of the tick, is tipped with pus. 

 When such a scab is removed a corresponding pit is seen in 

 the skin of the beast. The distribution of ticks, tick sores 

 and exudate on the skin of a beast is very irregular. For 

 instance, a fold of skin three by two inches on the escutcheon 

 •of the cow Fairy was carefully drawn to shew such distri- 

 bution. About two-thirds of the area was occupied by small 

 dry yellow granules and six larger hard red scabs, while 

 one nymph was present ; the other third contained two pairs 

 of ticks — adult and female (unbloated) — each pair being 

 attached to an inflamed area of skin. In close proximity 

 were an adult male and a nymph creating no disturbance. 

 An area of similar size, was examined on another cow, 

 Baby ; several dozen larvae (apparently just attached) were 

 visible, but, while the larvae were concentrated at two 

 points, dr}^ yellow granules were just as abundant in the 

 intervals as around the larvae. Three typical tick sores 

 were present as well as some hard dry scabs. Such instances 

 •could be multiplied indefinitely. 



A type of tick sore quite distinct from that described 

 above, is found on certain cows, notably Kittiwake. These 

 might be termed tick-blisters, as each forms a little rounded 

 -excrescence on the skin, filled with Ij^mph. These seem to 

 form usually round the point of attachment of a larval 

 or nymph tick, 



*AV. Herms (Jour. ParasitoL, 2. 191(i, p. 140), has givon an account 

 of tho tick sores produced by Ornithodorus coriaceus. Ifo mentions the 

 presence of lymph exuding from the wounds. 



