350 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1952 



transporting from one State to another, sheep affected with scabies; 

 and required, moreover, that all sheep shipped from stockyards to 

 other States for feeding purposes be dipped in some preparation that 

 would kill the mites. These devices alone did not show sufficient' 

 promise, however, in accomplishing the desired results. Even station- 

 ing of inspectors at shipping points in western States and at public 

 stockyards to supervise dipping was insufficient to make a significant 

 dent in the extent of the disease, or to sharply curtail its dissemination. 

 It was not until a Federal quarantine was placed on all the territory 

 west of the eastern borders of North Dakota, South Dakota, Kansas, 

 Oklahoma, and Texas— an area covering 1,700,000 square miles— 

 that a promising plan for extirpating sheep scabies from the United 

 States actually got under way. 



Under the new plan, inspections of sheep for evidence of scabies 

 were made systematically on the farm and range. Treatment by dip- 

 ping, under governmental supervision, in medicated solutions of 

 established efficacy was also required for all flocks that were affected 

 with, or had been exposed to, scabies. This plan, initiated in 1905 

 and still in effect today to a limited extent, resulted in the eradication 

 of scabies from sheep in areas of this country where it was once wide- 

 spread, and in reducing it elsewhere. 



In 1898, Salmon and Stiles, in a publication on sheep scabies, re- 

 viewed critically the dips then in use, reported their own experiments 

 with dips, and settled on two, namely, nicotine and lime-sulfur. 

 These two dips have been used successfully ever since 1905 in millions 

 of dippings. During the past few years the Zoological Division of 

 the Bureau of Animal Industry developed a dip that, in many ways, 

 is superior to, and much simpler to use than, the two that received 

 official sanction. The active ingredient of the new dip is one of the 

 chlorinated hydrocarbon insecticides, hexachlorocyclohexane, gen- 

 erally referred to as benzene hexachloride, or BHC for short. This 

 chemical has been standardized for scabies eradication, on the basis 

 of its gamma isomer content, to provide a margin of safety that should 

 meet most of the likely contingencies that are apt to arise. The new 

 treatment is rapidly gaining the approval of sheep producers and 

 livestock sanitary officials. Through its use, the relatively small 

 residue of what was once the most debilitating disease of ovine stock 

 can be eradicated, I believe, in much less time than with the old 



treatments. 



TRICHINAE IN SWINE 



When Joseph Leidy reported in 1846 to the Academy of Natural 

 Sciences of Philadelphia the occurrence of trichinae in the superficial 

 part of the extensor muscle of a hog, he inadvertently took the first 



