MECHANICAL DISTURBANCE BY PARASITES. 127 



the great clinical importance of Dochmius duodenalis (Anchylosto- 

 mum, Dub.) (Fig. 10), which occurs in masses in man in many tropical 

 and sub-tropical countries, and in the north of Italy, and is generally 

 so full of blood that at first sight the intestine of the patient appears 

 to be covered with leeches. As a rule, the presence of this worm soon 

 produces an anaemic condition. 1 This disease, with many others re- 

 sulting from it, is so common in Egypt, that nearly a quarter of the 

 native population suffer from it (hence " Chlorosis JSgyptiaca "), and 

 many perish for want of proper treatment, which ought of course, 

 in the first place, to be directed towards the removal of these danger- 

 ous guests. In this case we have, of course, to consider not only 

 the loss of blood which the parasites cause in filling their digestive 

 apparatus, but that which results from the bleeding of wounds caused 

 by their bites, which, according to Griesinger, 2 is often very con- 

 siderable. It is in this way that even leeches may become dangerous, 

 or even fatal, to man. 



At this point it may also be mentioned that a very considerable 

 loss of blood may be caused by the haematuria produced by the 

 wandering of embryos, as in the case of Filaria Bancrofti (F. sanguinis 

 hominis) and of Distomum hcematobium. 



But, on the whole, the disturbances resulting from the loss of 

 strength, and interruption of the nutritive supplies, are considerably 

 less than those which are occasioned by the growth and multiplication 

 of the Helminths. 



As soon as the worms exceed a certain size, they begin, like other 

 foreign bodies, to exert a pressure on their surroundings, which in- 

 creases with their size and with the inability of the surrounding struc- 

 tures to resist it. The influence of this pressure is, of course, most 

 frequently felt in the case of the larger parasites, and especially 

 in the case of those which have taken up their abode in narrow 

 channels or in parenchymatous organs. The parts which are most 

 immediately exposed to the pressure begin to lose their character 

 and normal appearance at the points of contact with the foreign 

 bodies. The canals mnst widen when the size of the inmates exceeds 

 their normal diameter. They form sinuses, and, if the circumstances 

 permit, even change into closed sacs, which become thicker and 

 thicker through hypertrophy of the connective tissue, until they can 



1 In individual cases years may elapse before the disease breaks out in full vigour. 

 The case of a workman in Vienna, who six years before had been a soldier in garrison in 

 the north of Italy, led Henschl to suppose that Dochmius duodenalis, like the D. trigono- 

 ccphalus of the dog, lives at first on epithelial cells, and only after they are exhausted 

 betakes itself to the vascular connective tissue of the intestinal villi (Mittheil. d. Vereins d. 

 Aerzte in Niederostcrreich., 1875). 



* Vierordt's Archiv f. physiol. Hcilkunde, Bd. xiii., p. 554, 1855. 



