134 VETERINARY STUDIES 



find the mites where the skin is greasy and glistening, and not 

 where the skin is dry and dull. It should be borne in mind 

 when examining a case of head scab that the mites which cause 

 this disease burrow beneath the surface of the skin, so that it 

 is necessary to scrape deeper than for ordinary body scab. 



Possible mistakes. — It is well to bear in mind, also, that other 

 conditions may be mistaken for sheep scab, particularly dis- 

 orders of the skin produced by other external parasites, such 

 as lice and sheep ticks. These are easily seen and they do not 

 cause any marked local lesion. Skin thickening is quite char- 

 acteristic of scab, but not in the case of ticks or lice. In the 

 so-called "wild fire" of sheep in northwestern states, the skin 

 is red, but not thickened and hardened as in scab. Occasionally 

 we have outbreaks of skin disease among sheep which on super- 

 ficial examination resemble scab rather closely. These outbreaks, 

 however, are due to the awns of a wild grass (Stipea sparta). 

 These spearlike bodies gradually work their way through the 

 wool into the skin, causing inflammation of the skin and con- 

 siderable irritation. 



Teeatment 



Suggestions. — Treatent is comparatively easy where there are 

 but few sheep, but it is more difficult with large flocks. The 

 size of the tank, material to be used, and method of dipping 

 must depend upon the number of sheep, and the accessibility 

 and expense of different materials. 



The dipping, as a rule, should not be done immediately after 

 shearing. It is better to wait a week or ten days. Some good 

 may be accomplished without shearing if the wool is parted by 

 hand and care taken to get the medicine down to the skin, but 

 it is the usual experience that dipping unshorn sheep is much 

 less satisfactory. 



The entire flock must be dipped, those that are apparently 

 sound as well as those that are diseased. And the owner must 

 bear in mind that after shearing, the wool may be a source of 

 danger, and that it should be so kept and handled as to avoid 

 the possibility of reinfection. 



Dipping is effective only when it is thoroughly done and 

 properly repeated. Lime and sulphur, coal tar dips, tobacco 

 and arsenic are the various ingredients that are commonly used 

 in dipping for scab. The quantity of dip required per sheep 



