LOSS OF NUTRIMENT BY THE HOST. 125 



larger masses, and that if only a moderate number be introduced, 

 hardly any disturbance of health will take place. 



But perhaps the overwhelming number of parasites by which 

 man is liable to be attacked will be best realised when we state that, 

 in cases of the so-called "Cochin-China diarrhosa," the number of 

 Rhabditis stercoralis which have been known to be evacuated in indi- 

 vidual cases, within twenty-four hours, amounts to several hundred 

 thousand or even to a million. ^ 



Three points have to be noticed in regard to the way in which 

 parasites affect their host. In the first place, they grow and breed at 

 the expense of their host, from whom they thus abstract nutritive 

 material. Secondly, they produce alterations in space as they press 

 upon the surrounding tissues or obstruct the channels in which 

 they live. Lastly, their movements, according to circumstances, 

 may give rise to pain, to iniiammation, varying in degree and in 

 termination, or even to perforation and dissolution, — all which 

 symptoms are, however, sometimes merely the result of continuous 

 pressure. 



The first of these three kinds of influence, although perhaps the 

 one which occurs most frequently, is seldom of much pathological 

 importance. There must be unusual influences at work, if the loss 

 caused by the abstraction of nutritive material by the parasite for its 

 metabolism, growth, and propagation is at all appreciable to the 

 host, provided that he belong to the larger animals, and much exceed 

 his parasites in size and nutritive requirements. 



A Bothriocephalus lahis, seven metres in length, weighs about 27"5 

 grms. According to Eschricht, it throws off yearly a number of pieces, 

 which measure altogether about 15 to 20 metres, and may represent a 

 weight of about 140 grms. Even on the supposition that the animal, 

 which of course undergoes continuous metabolism, abstracts three or 

 four times that quantity from its host,^ and that the nutritive 

 material consumed by all the parasites amounts to several pounds 

 yearly, it is easy to see that so moderate a quantity is of hardly any 

 account compared with the yearly consumption of the host. It is 



' Normand, " Mem. sur la diarrhce dite de Cochin-Chme, " Paris, 1877, and Davaine, 

 loc. cit., 2ded., p. 968. 



'' It does not require much proof to show that Heller's method of determining the 

 host's loss of nutritive material simply by the bodily weight of the parasites is erroneous. 

 (Art. " Darmschmarotzer " in "v. Ziemssen's Handb. d. sp. Path. u. Ther.," Bd. vii., 

 Th. 2, p. 567; Eng. transl., -'Cyclop. Pract. Med.," vol. vii., p. 678, London, 1877.) 

 Moreover, there are some tape-worms whose. growth is so rapid that Heller's method 

 also would give extraordinary results. The tape-worm of the sheep, for example, which 

 grows to the length of a hundred metres, has been found fifty-one metres long in lambs 

 four weeks old. — Goze, " Versuch einer Naturgesch., u.s.w.," p. 371. 



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