424 GROWTH AND STRUCTURE OF T.ENIA SAGINATA. 



This power is due to the strong development of their musculature, 

 which ensures a considerable mobility. This muscular development 

 is shared of course by the whole body, and contributes not a little to 

 the thick and fat character which we have already repeatedly 

 emphasised as one of the characteristics of T. saginata. Even after 

 leaving the intestine the proglottides retain for a while their mobility, 

 and creep about in a definite direction till the continued lowering of 

 temperature brings them to a stand-still. In lukewarm water their 

 movements can be followed for hours. They move just like indepen- 

 dent organisms, and were indeed formerly regarded as such ( Vermcs 

 cucumerim). In the warmth of the bed they often creep over the 

 whole body, especially if the skin be somewhat damp. The pro- 

 glottides which Pallas detected on the wall, more than a yard above a 

 patient's bed, were probably those of T. saginata, and not those of the 

 less muscular T. solium. 



Although it is always only the last and oldest joints which 

 become separated from the chain and wander outwards, they are by 

 no means always the largest. This is due to the fact that they 

 generally lose a more or less considerable portion of their contents 

 just when the separation commences, and are indeed occasionally 

 liberated almost destitute of their eggs. As a rule, it is at the anterior 

 border of the joints that the eggs escape, which is explained by the 

 circumstance that it is at this point that the uterus, with its longi- 

 tudinal canal and lateral branches, is most closely approximated to 

 the surface, and is therefore most easily ruptured by the pressure of 

 the contracting muscles. While the joint creeps about, the eggs are 

 sometimes seen issuing in a stream from this point. 



The decrease in size which ensues in consequence of the expulsion 

 of the eggs, expresses itself in a diminution of the transverse diameter, 

 which is sometimes (Fig. 237) contracted to less than 4 mm., and oc- 

 casionally so much that the proglottides look quite cylindrical. Empty 

 joints of this rounded form have been repeatedly sent to me as " thread- 

 worms," although the nature of their body-parenchyma, and the 

 constant distinctness of the lateral ridges, made their true nature 

 at once obvious to the expert 1 . 



So long as the animals retain their mobility, one can observe a 

 perpetual change of form ; they are at one time stretched out and 

 nearly cylindrical, and again they are contracted into a club or flask- 

 like form, till finally they become short, flattened, broad, quadrangular 

 bodies, still possessing a quite appreciable thickness, and recognisable 

 in form and character as tape-worm segments. Throughout these 



1 Even a helminthologist must be reproached with having confused these joints with 

 Oxyuridse ; see Coulet, " Tractatus de Ascaridibus et Lumbrico lato : " Lugd. Bat., 1729. 



