1 66 Veterinary Medicine. 



commonly used and showing the time taken by each to kill the 

 acarus apart from the body. The application is general to 

 scabies in all classes of psoric acari and their hosts. 



In making a selection from such a list we must consider the 

 fixed or volatile nature of the agent. Such agents as benzine, 

 naphtha, petroleum, prussic acid, etc., though very deadly to the 

 acarus, volatilize so rapidly that they are on the whole less relia- 

 ble than mercury or sulphur, which are among the very slowest 

 acaricides. The less volatile products of the distillation of wood 

 and coal tar, such as oil of tar, creosote, and many of the more 

 modern products (hydronaphthol, benzonaphthol, naphthol, 

 naphthalin, chloronaphtholeum, creolin, cresylol, cresyl, lysol, 

 aseptol, etc.), are more trustworthy even when they act much 

 more slowly on the parasite. This applies with especial force to 

 the sarcoptes which, hidden in their galleries, escape the volatile 

 agent, and when they do come out of their burrows somewhat 

 later, find themselves unharmed, the deadly agent having evap- 

 orated. In regard to the eggs to be hatched a few days in the 

 future the same is true. When they open the shell, the deadly 

 but volatile agent has disappeared, while the more .stable, even if 

 less deadly, agent remains ready to destroy them. For sarcoptes 

 the very volatile agents would require renewed applications at 

 short intervals to catch the acari as they emerge from their holes, 

 and the larvae as they escape from the eggs. Benzine, naph- 

 tha and petroleum are further dangerous as irritants of the ex- 

 coriated skin, retarding healing and making recovery doubtful. 



Another consideration in dealing with domestic animals is the 

 use of an agent that will not poison the patient when he licks 

 himself. Tobacco, a slow acaricide is yet very lasting and effec- 

 tive and may be used freely on the ruminants and even the soli- 

 peds, which have almost no susceptibility to nausea. In carui- 

 vora on the other hand it would cause violent nausea and vomiting 

 and dangerous illness. Arsenic and Mercurial preparations kill 

 the acarus slowly, yet being comparatively non-volatile one appli- 

 cation is lasting and efficient. But any animal licking and 

 swallowing these will be poisoned, perhaps fatally. Even apart 

 from this they are liable to be absorbed through the raw or 

 excoriated skin, to be swallowed as drink, or to be washed off 

 during rain on to the pasture and taken in with the food. Of the 



