650 MANAGEMENT OF SHEEP EXTERNAL PARASITES 



results as supplementary ingredients ; and corrosive sub- 

 limate (perchloride of mercury) is recommended by Finlay 

 Dun l as a cure for scab. This last, however, is so much 

 more dangerous to the animals than arsenic that it is rarely 

 resorted to. 



A dip made with white arsenic (rendered soluble by boil- 

 ing in 2.5 gallons of water 45 Ibs. of commercial arsenic 

 (As 2 O 3 ) with 45 Ibs. of carbonate of soda crystals, to form the 

 arsenite of soda, 2 without leaving any free alkali) is immedi- 

 ately effective in destroying the mature acari of scab, 

 although it is harmless against the young forms, which hatch 

 out from the uninjured eggs in a few days after dipping. It 

 is not dangerous to the sheep if used in moderate quantities, 

 say 2 Ibs. to 100 gallons of water. A case is recorded of sheep 

 losing their teats after being dipped in a solution of double 

 this strength. It is best for the farmer to purchase arsenic 

 in solution, which can be got at two shillings per gallon, each 

 gallon containing 5 Ibs. of arsenic. Cold water is then added 

 to the concentrated liquid, to reduce the solution to the 

 standard strength. 



Sulphur is commonly used in this country in the insol- 

 uble form of the flowers of sulphur, which merely mixes 

 with the other dip materials. It adheres to the wool and 

 exercises a prolonged influence the odour evolved keeping 

 off maggot-flies during summer. Whether administered in- 

 ternally or applied externally, it is extremely searching in its 

 action, and its presence is inimical to the development of 

 most of the common forms of ovine parasites. Its chief 

 drawback is the difficulty of mixing it in the dip so that each 

 sheep shall receive a proper proportion. This is partially 

 overcome by associating with it an equal weight or more of 

 black (soft) soap, which also aids in dissolving arsenic. In 

 Australia, where sulphur has been most effective when skil- 

 fully handled in the extermination of scab, and in America 

 and South Africa, where it has been skilfully handled and 

 largely used, it is dissolved in combination with lime 25 

 Ibs. of sulphur and 18 Ibs. of slaked lime being made into 

 the consistency of thick cream, and then boiled for twenty 



1 Veterinary Medicines, 8th ed., 1892. 



- Cold water is then added to bring the amount up to 9 gallons of a 

 standard solution containing about 5 Ibs. arsenic per gallon. 



