PREVENTIVE MEDICINE 367 



undoubtedly checks the flow of scab into this country, but, as has 

 been pointed out, portal inspection cannot be expected to detect all 

 cases of scab infection. It therefore serves as a check but not 

 as an absolute preventive. 



Sheep-scab having appeared among a flock dipping is impera- 

 tive. One dip is useless, and it is more than doubtful if a double 

 dipping, the second taking place 10 days after the first, can be 

 regarded as a certain safeguard against re-infection. A flock of 

 sheep dipped in a perfunctory manner is a serious danger to the 

 sheep breeding industry as there is always the danger of infec- 

 tive animals remaining which may start the disease afresh in the 

 flock, or, what is worse, be the means of starting the trouble in 

 a fresh area. 



Concurrently with the dipping of infected animals attention 

 should be paid to the various indirect media of contagion. Gate 

 posts, hurdles, rubbing-posts and other things likely to have come 

 in contact with the sheep must be cleared of wool and treated with 

 a disinfectant. A suitable disinfectant for this purpose is limewash 

 containing 5 per cent, of carbolic acid. The whitewash serves a 

 useful purpose by indicating what parts have been treated with 

 the carbolic and what have been missed. 



Sheep Dips. There are more than 500 sheep dips that have 

 been approved by the Board of Agriculture. Every dip used under 

 the Sheep-Scab Order (see page 385) for the compulsory dipping 

 of sheep, whether they are diseased or not, must be approved by 

 the Board as suitable. A large number of the proprietary dips 

 are convenient to mix and handle as well as being efficient. A dip 

 is more efficacious on shorn sheep than on those with long fleece. 

 Dipping is done with greater safety a fortnight or so after shearing, 

 as this allows the sheep to get accustomed to the loss of their cover- 

 ing and gives time for any cuts and abrasions to heal; this is not 

 unimportant, as many of the dips contain poisons that might be 

 absorbed through the broken skin. Dipping should not be done 

 on a rainy day as the dip would then be washed off too soon; 

 neither should sheep be exposed to the dip when they are thirsty 

 or very hot ; if rounded up from any distance in hot weather time 

 should be allowed them to cool off. Dipping tanks or baths are 

 made of various styles and sizes to suit local requirements. The 

 two chief types are the small hand bath and the swim bath. The 

 former is used where small lots of sheep are to be dipped, and the 

 latter when the flocks are large. Though small hand baths are 

 economical to build they are extravagant with labour, and the 

 work is hard on the men when the dipping is being done, and there 



