2 AUTHOR'S PREFACE. 



The investigation of the natural history of the intestinal worms, 

 at the same time, opened up a channel through which their mode of 

 origin could be traced ; and indicated a way in which the attacks 

 of those parasites which are dangerous or troublesome to man 

 and animals, could be prevented; an object, in certain cases, of 

 the highest importance, since the morbid changes induced by 

 many entozoa in the organs which they infest, are not always 

 removable. 



For a long period, I have been at much pains to inquire into 

 the origin of the entozoa found in man and the domestic animals ; 

 and in the present essay I lay before physicians, veterinarians, 

 and breeders, a summary of the results of the observations 

 and experiments which I have made upon the production and 

 development of these creatures. My chief attention has been 

 directed to the destructive cystic-worms, and I believe that the 

 conclusions at which I have arrived are not merely a gain for 

 science, but promise to be of useful practical application. 



MUNICH ; March 30/A, 1854. 



