MODE OF ACTION OF ANTHELMINTICS. 219 



Purgatives, and especially drastic purgatives, 

 expel the worms by increasing the iatestinal secre- 

 tion, and by exciting the peristaltic movements of 

 the intestine ; they have for a long time constituted 

 the principal medicines used in the treatment of 

 intestinal entozoa, and they are frequently combuied 

 with substances which have a special vermifdge 

 action. 



The vermifuge remedies, that is to say, those 

 which act upon the worms themselves, appear to 

 do so, either by an actual poisonous effect upon the 

 parasites, or by making their habitat offensive to 

 them, as when assafoetida is administered, for 

 instance. 



The action of anthelmintics can only be correctly 

 judged by observations of their effects upon man or 

 upon animals. The trial of these remedies upon 

 entozoa which have been removed from their natural 

 habitat, cannot be depended upon, as they perish 

 quickly, when they have arrived at the adult state, 

 and it is difficult to estimate the relative share which 

 the lowered temperature, the removal from their 

 usual habitat, and the substance experimented with, 

 have in causing the death of the worms. The 

 numerous experiments which have been made by 

 different observers are consequently of uncertain 

 value. 



The therapeutic agents which are used as anthel- 

 mintics do not possess an equal action upon all the 

 intestinal entozoa, and most of them have a more 

 marked influence upon certain species than upon 

 others. 



The following list, in which an alphabetical order 



