g6 OF THE PRINCIPAL WOllMS 



ly describes, and wliich, from their Large size, have 

 by some been considered as a different species. (31) 



The diversity of the external structure of the 

 taenia of the same species, does not depend solely 

 on the difference of a2;e. 



The nature of the soil, climate and food, vary- 

 ing in different countiies, explains the great influ- 

 ence which produces the changes and varieties of 

 form of all living beings. 



It is thus, as I believe, that the natural consti- 

 tution of the animal structure, which we see alter- 

 ed in a thousand ways, contributes much more 

 than is commonly supposed, to the variation of the 

 exterior forms of the taeniae of the same species. 



In fact, the inliabitants of the north are much 

 more subject than other people to the gray taenia ;(3S) 

 the Swiss to the flat taenia ; the Italians and the 

 inhabitants of Lower Saxony to the taenia cucurbi- 

 tina, etc. The feebleness or strength of the pa- 

 tient, the soundness or diseased state of the worm 

 itself, are circumstances which affect the size, soft- 

 ness or fiirraness of the worm, and its development. 



The winding of the intestinal canal, the pres- 

 sure of the contiguous viscera, and other similar 

 accidental causes, obviously aff'ect the growth of 

 some portion of the taenia. 



^ VIII. We have no exact description of the 

 interior organs of this worm. (33) 



We only know that it belongs to the class of 

 oviparous animal?, because in every joint there is 

 an ov.n y of a peculiar nature, sometimes having 



