98 THE INTERNAL PARASITES OP 



particles (c), which the old naturalists formerly supposed 

 to be eggs. The common bladder vesicle from which 

 the heads project exhibits cellular markings. 



The above figures are copied from Numan's treatise, 

 and I can testify to their perfect accuracy of detail. In 

 one remarkable instance, recorded by Eichler, as many 

 as 2000 heads were displayed by a single coenurus. 



It must be evident to any thinking person that the 

 results thus obtained by scientific research are of the 

 highest value, and so complete a knowledge as we now 

 possess should place us in a position to utilise these 

 results with practical advantage. In short, we can either 

 increase or decrease the number of parasites and the 

 diseases they create according to our desire. If a crop 

 of these parasites could be shown to be beneficial, their 

 production might be favoured by experiment to a prac- 

 tically illimitable extent ; but, as no very obvious good, 

 whilst much harm, is clearly traceable to their prevalence, 

 it is manifestly our duty either to put a check upon their 

 increase, or to obliterate them altogether. The question 

 therefore is, " How shall we proceed V 3 The reply must 

 be, " Destroy the tapeworms and their ova." 



It is not sufficient that the sheep farmer should look 

 closely after his flocks, guarding against the bad effects 

 of excessive cold, wet pasture land, coarse fodder, and so 

 forth. These precautions (admirable in themselves, 

 and essential to the prevention of other maladies than the 

 particular one in question) have no power in warding off 

 epidemics of gid. 



What the advocate of agricultural hygiene has to insist 

 upon is the cutting off of the supply of those tapeworm 

 eggs which, by their introduction into the fodder, form 

 the sole cause of gid. To thrust this scientific conception 



