^92 A TICK-RESISTANT CONDITION IX CATTLE. 



(Thorn, R.S.C., p. 28). The only fair way to test resistance 

 is — as has Leen eniphasied by Mr. Cory, Chief Inspector 

 of Stock, Queensland (R.S.C., p. 53, 54) — to place such 

 animals on natural pastures where ticks are known to be 

 present and then note whether the parasites mature on those 

 •cattle. 



On one occasion the strongly resistant cow PeeweCj 

 and her young calf (five months old) were running with 

 ticky cattle elseAvhero for some months. On their return 

 to Eumundi the former was clean while the calf Mas tick 

 infested. 



So that the relationship of the various resistant animals 

 belonging to Mr. Hull's herd might be more easilj'^ seen, 

 we append a genealogical table (pp. 293-5). In the case of 

 Peony it will be noticed that the peculiarit\' has persisted 

 to the fourth generation. 



Tick resistance appears to us to be a quality capable of 

 hereditary transmission but like many other qualities it 

 may or may not be inherited. We know nothing regard- 

 ing the tick i-esistant qualities (if any) of the male parents 

 and consequently it is impossible to discuss the tables 

 satisfactorily. 



We know that natural immTinily to disease is a hei'e- 

 ditable quality both in animal and plant life. 



It is likely that some strongly resistant animals which 

 are known to occur in many herds are to be regarded as a 

 mutation in so far as this particular character is concerned, 

 and if such be the case then its inheritability is to be expected. 

 Before concluding that a resistant calf from a resistant 

 parent (no matter how such resistance were attained) has 

 inherited such quality, one must remember that it has 

 been proved in the case of resistance to bacterial invasion, 

 that anti-bodies formed in the maternal blood may be 

 transferred through the placental circulation to the blood 

 of the offspring, the latter thereby becoming resistant or 

 immune to such invasion for a period of some months after 

 birth, but subsequently losing such resistant power. Before 

 such loss occurred, it might be possible for the animal to 

 have acquired protection naturally, i.e., to have elaborated 

 its own anti-tick bodies in response to continual stimulation 

 by larval tick attack, so that the immunity becomes an 

 active one. 



