DISTRIBUTION AND MEDICINAL SIGNIFICANCE. 729 



resembles that of the adult form. It can at the most be said that its 

 musculature is inferior in development and strength. But this is 

 only true when the developed joints are included in the comparison, 

 for the neck of the Bothriocephalus — and, as may be readily conceived, 

 only this ought to be compared with the larval body — presents hardly 

 any characteristics beyond those exhibited by the bladder-worm from 

 the pike. Even the musculature of the head of the larva, when 

 protruded, exhibits exactly the same relations as subsequently, and 

 consists of direct prolongations of the longitudinal fibres of the body. 



Distribution and Medicinal Significance. 



While the large-jointed Tcenice of man, and especially T. saginata, 

 may almost be regarded as cosmopolitan parasites, the distribution of 

 Bothriocephalus latus is much narrower, and its occurrence more 

 restricted. It has hitherto been observed with certainty in but few 

 places outside Europe. According to Verrill, it is found, though but 

 rarely, in North America, and, according to Baelz and Ijima, it is 

 frequent in Japan. In Europe, moreover, it only occurs in certain 

 countries and districts. The most noteworthy localities are the coasts 

 of the Baltic, especially the more easterly, and Switzerland, particu- 

 larly the west. As is well known, the latter country furnished the 

 first instance of Bothriocephalus. According to Zaeslein,^ to whom 

 we owe very thorough information regarding the occurrence of Bothrio- 

 cephalus in Switzerland, the worm was formerly principally confined 

 to the shores of the Lakes of Biel, Murten, Neuenburg, and Geneva. 

 These localities may still be described as the principal seats of the 

 parasite, although in some places — for example, in Geneva, where, 

 according to Odier, a fourth of the population suffered from it — it has 

 in the course of time become much less frequent. On the other hand, 

 there are still places on the shores of these lakes (for example, Nidau, 

 on the Lake of Biel) in which one adult out of every five suffers from 

 this tape- worm. Children under ten are usually exempt. Some 

 leagues (not more than four) from the water, Bothriocephalus is found 

 much less frequently, especially among an agricultural population. 

 The same is true in a greater degree of the more distant parts of the 

 surrounding country, for there the worm appears only in the towns, 

 usually in consequence of transference, and is only in a few places 

 (Burgdorf and Thun) autochthonic. In the rest of Switzerland Bothrio- 

 cephalus only occurs sporadically, although there may be no want of 

 lakes abundant in fish. Huss^ reports that among the sea-coast popix- 



1 Cmrespondenzblatt fur schweizer Aerzte, Jahrg. xi., p. 673, 1881. 



2 " Ueber die endemischen Krankheiten Schwedens : " Bremen, 1854. 



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