PEE FACE Vll 



der Helminthologie, which, for the purposes held in view by the 

 author, leaves little to be desired. 



Expressly to meet the requirements of the Sanitarian I 

 have dwelt upon the developmental phenomena exhibited by 

 those parasites that occasion fatal helminthiases ; and, in this 

 relation, I have not confined my remarks to the parasites that 

 are injurious to man in a direct manner, but have extended my 

 observations to the genesis of those entozoa that prove destruc- 

 tive to horses, to beasts of burden generally, and to other 

 creatures which, like cats and dogs, are in various ways sub- 

 servient to man's wants. It will be seen that in this way 

 several questions relating to the purity of water and flesh- 

 food, respectively, have been incidentally brought under notice. 



In view of the magnitude of the task which my enthusiasm, 

 perhaps unwarrantable, has led me to undertake, I know full 

 well how considerately my foreign friends and correspondents 

 will deal with the errors of omission and commission that they 

 will certainly detect in these pages. If there be any educated 

 persons at home who still affect to despise the revelations of 

 helminthology, I can assure them that their prejudices are 

 misplaced. The study of the structure and economy of a 

 humble parasite brings to the investigator no slight insight 

 into the workings of nature. If these workings cannot at all 

 times be pronounced to be " good and beautiful," they must at 

 least be characterised as " true." The knowledge of the true 

 especially if that knowledge by its practical applications be 

 calculated to confer substantial benefits upon man and his 

 inferior fellow- creatures ought to be held in high esteem; but, 

 apart from this purely utilitarian view, there remains for the 

 investigator the delight occasioned by the in-rush of new scientific 

 ideas. The average mind, being either essentially commercial 

 or ridiculously sentimental, as the case may be, is totally inca- 

 pable of comprehending the motive power that animates and 

 guides the votary of science. The late Professor Faraday, a 



