' HISTOKICAL ACCOUNT OF CYSTICEECUS CELLULOSJE. 537 



We know, however, that the animal nature of the bladder-worms 

 was not detected till towards the end of the seventeenth century, nor 

 was it generally recognised till at a still later date (in consequence of 

 the researches of 0. Fabricius and Goze). Till then the bladder- worms 

 were regarded as tumours, closely allied to the encysted and glandular 

 tumours. In Oribasius and Aetius we find it stated that Androsthenes 

 compared them to tubercles, and that Aretseus compared measly pigs 

 to people suffering from elephantiasis. The fact, known even in 

 Aristotle's day, that new-born pigs bad no bladder-worms, seemed 

 quite to harmonise with the theory which sought to explain these 

 structures as diseases. 



Our knowledge of bladder-worms did not, however, attain any 

 completeness till the genetic relation between them and T. solium was 

 demonstrated. Then for the first time it was seen that the bladder- 

 worm disease, which had been formerly referred to bad food, such 

 as decomposing corn or acorns, or to infection and inheritance from 

 one pig to another, always originated from infection with the eggs of 

 the common hook-bearing tape-worm infesting man. Such an infec- 

 tion is greatly facilitated by the habits of the pig, which rejects neither 

 human excrement nor water from the dung-heap, and by the fact 

 that the joints of T. solium are always expelled with the faeces, 

 and sometimes hang together in numbers even after expulsion. 

 Thus it is explained that the bladder- worms of the pig are only rarely 

 found isolated, but usually live in companies, and sometimes in such 

 numbers that the flesh looks almost like frog's spawn. In the case of 

 an animal experimented on by Haubner, there were in one piece of 

 flesh about 17 grams in weight not fewer than 133 bladder- worms, 

 so that, supposing the distribution uniform, the total number present 

 in a mass of flesh weighing 20 pounds would be about 80,000. I 

 obtained similar results from one of my experiments, in which I 

 counted 250 bladder-worms in about 31 grams of flesh. 



Cases of such abundant infection are of course rarer in nature 

 than in experiment, but some might be cited where 15 grams of 

 iiesh contained about 30-40 bladder-worms, and where the total 

 number of parasites might be estimated at from 12,000 to 20,000. 

 The favourite situations of the worms are the breast and shoulder 

 muscles, the tongue, the diaphragm, and the legs. The gullet, heart, 

 and the subcutaneous tissue are also frequently inhabitated by 

 bladder-worms, as are also the nervous centres and eyes, while the 

 viscera are, as a rule, only rarely infested. 



The symptoms of disease vary according to the situation and 



number of the bladder-worms. When they occur but sparsely, and 



are restricted to the muscles, they occasion hardly any disturbance. 

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