GENERAL REMARKS. 55 



latter country ; and the existence of the bothrio- 

 cephalus latus has been satisfactorily proved in 

 Europe only. 



Some species of entozoa are, however, almost 

 universally diffused ; these are the taenia, the oxyuris, 

 and the ascaris lumbricoides. 



With respect to the greater relative frequency of 

 certain, species of worms in certain countries, that 

 of the taenia in Egypt, and in Abyssinia, for example, 

 is generally acknowledged ; that, again, of the 

 bothriocephalus in particular districts of Sweden, of 

 Kussia, and of Switzerland ; that of the ascaris 

 lumbricoides amongst the negroes, and also, that of 

 hydatid worms in Iceland. 



The influence of locality upon the existence of 

 entozoa depends upon various conditions of wliich 

 the exact ratio is usually very uncertain ; the climate 

 always appears to be the principal condition affecting 

 the existence of the filaria medinensis, and this is also 

 possibly the case with regard to the anchylostomum 

 duodenal e and the distomum haematobium. 



An influence which is less permanent, but which 

 is, in some respects, equal to that of chmate, is pro- 

 duced by the seasons. These bring with them varia- 

 tions of temperature, of moisture, and of diet, wliich 

 favour the development or transmission of certain 

 species of worms, and which consequently render 

 these species more or less common, according to the 

 different periods of the year. 



Amongst the conditions which are favourable to 

 the development of entozoa, and which are dependent 

 upon the climate or the season of the year, moisture 

 is one of the most apparent. Prolonged rains ui 



