113 



heifers from another district showed a fairly heavy infestation. In the 

 opmion of the authors no stronger evidence could be adduced to prove 

 the presence of a very marked tick resistance in these anunals. In 

 practically all other cases examined or reported by others, these 

 animals retained their resistance even when moved to other districts 

 and did not require any treatment to prevent tick worry if they were 

 kept m fair or good condition, these being the first 3 points claimed 

 ongmally by Mr. Hull. Though departmental findmgs on 2 selected 

 cows were exactly the opposite of the above, it may be conceded that 

 they were probably correct when the animals were subjected to 

 abnormal circumstances, such as poor condition, intense artificial 

 infestation, etc. Further observations on the fertility of engorged 

 ticks from resistant animals showed the existence of some impairment 

 of vitality as proved by the lessened number of viable eggs. The 

 authors do not support the claun that the ticks on resistant cattle 

 have developed on other anunals and re-attached themselves, and 

 they explain the occurrence of the few ticks found in winter, when 

 other cattle are free, by the fact that these occurred on milkers, which 

 are frequently in low condition during winter ; they further found 

 that the registered temperatures of resistant cattle during summer 

 were approximately normal. 



In reply to a published appeal for observations by farmers [see 

 this Review, Ser. B, vi, p. 187] it is stated that Brahmin cattle and 

 crossbreds are more or less strongly resistant. In Queensland resist- 

 ance is not confined to any one breed but seems to be more common 

 anaong Jerseys and Jersey crosses, perhaps on account of their fine short 

 hair and oily skin. Individual animals of various other breeds and their 

 crosses may possess a marked resistance, due to individual idiosyn- 

 cracy. Resistance in animals from isolated localities, usually in the 

 vicinity of scrub country is perhaps due to the more abundant fodder 

 mamtainingthem in better condition. The claim that the application 

 of an arsenical dip or wash temporarily suppresses resistance does 

 not seem to hold good, provided that the condition of the animals 

 is not lowered by the treatment. 



After collecting all the available evidence concerning the hereditary 

 transmission of resistance by vaccination and by contact, the authors 

 conclude that in certain cases this does occur, "though they have not 

 succeeded in transmitting it by vaccination with exudate to any of 

 their experimental animals, nor has resistance developed in animals 

 kept in contact with resistant ones for periods varying from 

 1-7 years. 



They conclude that the condition is naturally ac'quired as a direct 

 result of moderate, long-continued infestation, which causes the 

 production of an anti-tick substance in the blood and other fluids 

 of certain cattle. In view of the greater probability of undipped 

 animals dying of tick worry than of becoming resistant, dipping in 

 conjunction with a rotation of paddocks should be systematically 

 carried out in order to control the ticks and assist in their eradication. 

 Associated with tick resistance there may be an exudate forming 

 small granular masses of thin flat yellow scabs, this condition appearing 

 to graduate into a type of tick-sore, so far noticed only on resistant 

 animals. The exudation makes its appearance particularly during 

 the warmer months (October to June), and especially during the 



