24 ANIMAL PARASITES 



them and their effect on the skin, provided they 

 have not continued their ravages too long, for 

 their careful treatment by those experienced in 

 cutaneous diseases is sometimes requisite to relieve 

 the patient of their trouble. We mean that se- 

 vere and persistent iuflammation of the skin is 

 often caused by the presence, and consequent irri-, 

 tation, of these animals we have described, call-' 

 ing for the best efforts of those who have made 

 diseases of the skin a special study, in order to 

 subdue it. 



The treatment oiphthiriasis^ or the presence of 

 lice, is quite simple, if three things are borne in 

 mind, namely : that we must kill the live insects, 

 destroy the eggs, and care for the condition of the 

 skin left afterwards. Now there are a number of sub- 

 stances of the mineral and vegetable world, which 

 are quite deadly to these animals when brought iu 

 contact with them, such as sulphur, mercury, seeds 

 of stavesacre, of sabadilla; the root of pyrethrum 

 or pellitory, many of the essential oils, and alco- 

 hol. All the patent medicines and other adver-j-, 

 tised nostrums warranted to destroy these vermim 

 contain some of these substances ; but as many 



