428 GROWTH AND STRUCTURE OF T^NIA SAGINATA. 



large tape-worm from the cat (which is not more muscular than the T. 

 saginata), six inches long, contract " with incredible rapidity" to a length 

 of a few lines, and the whole worm, after having been only three 

 inches long, when put into lukewarm water extended itself again to a 

 yard and a quarter.^ 



The contraction is not uniform over the whole length. One some- 

 times sees, indeed, that the whole worm shortens powerfully and 

 suddenly, if it be, for instance, rapidly transferred from the warm 

 intestine to cold water or spirits. Similarly, one sometimes sees a 

 wave of contraction pass continuously backwards or forwards over a 

 long series of joints. Not less frequently do we find that the play of 

 motion is confined to a short portion, or to a few joints, which thus 

 manifest before their separation that morphological and anatomical 

 independence which is also (see p. 293) expressed in the arrangement 

 of the muscles of the body. Not unfrequently one finds neighbouring 

 portions and joints in quite different states ; some broad and much 

 contracted, others long and drawn out into thin bands, and may even 

 observe that not only the anterior and posterior ends, but the two 

 sides of the same segment, are in form and motion somewhat inde- 

 pendent of one another. 



We need not emphasise the close connection between the number 

 of the ripe proglottides and the length of Tcenia saginata. The 

 number varies greatly in different cases. Even the number of pro- 

 glottides expelled daily from the affected patients may vary from seven 

 or eight up to twelve, although the growth is on the whole very uniform, 

 a head producing in about three months a chain of about 1300 joints, 

 and therefore about fourteen daily. It is thus evident that the number 

 of ripe proglottides would be continually on the increase, were it not 

 that there occurs from time to time a specially copious expulsion. - 

 On the other hand, we must also take into account that the formation 

 of new joints in the adult tape-worm will perhaps occur less rapidly 

 than was the case during the development of the chain, for in the 

 adult the relation of the nutritive absorptive surface to the growing 

 mass is ever becoming more unfavourable. It is possible, further, 

 that varying nutritive conditions may in some cases determiue an 

 unequal growth. 



The general growth and gradual increase in size of the joints, and 

 their influence upon the appearance of the worm, may be most con- 

 veniently discussed by taking a concrete example. I will, in the 

 first place, refer to a specimen in the collection at Leipsic, which 

 in a comparatively contracted state measures 485 cm., and is com- 



» Loc. cit., pp. 345-346. 



- This supposition is ooi^j^Q^^^^^ljiyi^-^^g^^^jj^^per's experience in Abyssinia. 



