The Sheep- Scab. 9 



scab corresponds with the itch in man, and 

 mange in dogs, the parasite is in each case a 

 different one, and the acarus which causes scab 

 in sheep will not cause either of the other dis- 

 eases, neither will the acari which produce those 

 diseases cause " Scab." 



The male acarus is smaller than the female, 

 and is migratory in his habits. One male suffi- 

 ces for many females, and is longer lived than 

 the female. The latter is of a sedentary nature 

 and may be more easily discovered than the 

 male. The adult acarus has eight legs, four 

 before and four behind, although of the latter, in 

 the male, the inner two are rudimentary. 



M. Walz, a German veterinarian, who has 

 given much investigation to the subject, has 

 graphically described the mode of operations by 

 these parasites. 



If a female acarus be placed on the wool of a 

 sound sheep, it quickly travels to the root of it, 

 and buries itself in the skin, the place at which it 

 penetrated being scarcely visible, or only distin- 

 guished by a minute red point. On the tenth or 



