610 DEVELOPMENT AND GKOWTH OF TiENIA SOLIUM. 



however, that it might not sooner undergo a metamorphosis into a 

 tape-worm. Since it is not the whole cylindrical body of the worm, 

 as we shall afterwards see, but only the head proper, which becomes 

 the tape-worm, a shorter time is sufficient to render the transforma- 

 tion possible. After the lapse of two months and a half the head is 

 provided with hool^:s and suckers, and we may even- conclude that 

 the bladder-worm of the pig attains maturity before the close of the 

 third month. The subsequent changes are hmited essentially to an 

 elongation of the cylindrical body. According to all appearances this 

 increase in length is not in any way restricted to a certain age, though 

 in course of time it gradually decreases in rapidity. Even the bladder 

 sometimes increases for a while in size, though usually (and particu- 

 larly in the muscles) it is but little larger than a small bean. 



It is difficult to determine accurately how long the bladder-worm 

 may live and retain its potentiality of development. In the case of 

 bladder-worms from human muscle, Stich ^ believes, though on the 

 strength of but few and uncertain observations, that from three 

 to six years may elapse. After this period the bladder-worms, 

 easily detected through the skin, lose their elastic character, and 

 one after the other gradually become smaller, and finally dis- 

 appear, on superficial inspection at least. The bladder - worms 

 inhabiting other organs, especially the brain and eyes, may indeed 

 attain a much greater age. There are cases of bladder-worms in 

 the brain which have for twelve to fifteen years excited the most 

 critical symptoms,^ and by help of the ophthalmoscope a bladder- 

 worm in the vitreous humour has been observed and demonstra,ted for 

 twenty years." 



It is no longer necessary to give any special proof of the identity 

 of the common bladder-worm of the pig with this bladder-worm 

 occurring in man,* the most careful scrutiny reveals no difference 

 between them, and their mode of origin is the same. It does not 

 follow, however, that it is always and only the Gysticercus cellulosm 

 which infests man. In fact we shall afterwards find that another 

 bladder-worm occurs in man under like conditions, and represents 

 no mere variety, as is the case with other forms, which both 



^ Stich, Annalen des Charitc-Krankenhauscs, p. 170 : Berlin, 185i. For Lewin's 

 criticism, loo. oit., Bd. ii., p. 645, 1875. 



'' See Lewin, loc. cit., p. 645. 



' Zulzer, Klin. Wochenschr., No. 4, 1876. 



* This special proof has been furnished by Redon, who s-wallowed four human bladder- 

 worms, and three months afterwards voided proglottides of Tcenia solium. Redon over- 

 estimates, however, the importance of his experiment, when he asserts that the identity 

 of the human bladder-worm with the Cysticercus cellulosm was thus for the first time 

 established. (Comptes rendus, t. clxxxv., p. 676, 1877.) 



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