TRICHOCEPHALUS DTSPAE. 325 



This worm has been found in Europe and Africa in children and 

 adults, and probably occurs also in other parts of the world. 



Anatomy and physiology of the worm. — Of the form of the 

 body we shall speak presently ; we commence with the 

 skin. In both males and females it consists of transverse 

 rings (Wedl) passing into each other, which are formed of the 

 well-known chitinous substance, colourless, and, to a certain 

 extent, elastic. On the free margins these are somewhat pointed, 

 or appear rather rounded when seen from the surface, by which 

 the worm acquires sometimes a more undulated, sometimes a 

 more serrated appearance. Moreover, fine, small elevations, some- 

 times round (like warts), sometimes acute (like spines), run 

 round the animal upon the epidermis, which Wedl has indicated 

 in his figure 191 h, and which I also think I have seen in some 

 specimens, especially on the anterior part of the body, but 

 which I have omitted to figure, both on account of their indis- 

 tinctness, and because they would easily have destroyed the 

 clearness and intelligibility of the figure. As far as I could 

 make out, these little warts and spines are only retained in 

 patches upon the worm, and very readily fall off from spaces 

 of considerable extent. However, any one can easily form an 

 idea of them for himself, if he imagines the whole body covered 

 with the same coat of hooklets, which we find upon the copu- 

 latory organ of the male. Here they remain longest, and 

 perhaps are more persistent in this part because this organ is 

 retractile, and therefore much less exposed to external friction, 

 &c, than the general epidermis of the animal. Here, therefore, 

 we have an analogue of what we have seen in the Trematoda, 

 when speaking of the penis of Distoma hepaticum. 



In treating of the skin we have still to speak of the longitu- 

 dinal streak which runs down on each side of the worm, and which 

 is particularly distinct upon the anterior part of the body, but is 

 also present upon the abdomen, and which has had very various 

 significations given to it by different authors. Dujardin refers 

 to it in these words : " Tegument strie transversalement, avec 

 une bande longitudinaleherissee de petites papilles." The little 

 papilla? are an attribute of the entire skin, as we have seen ; 

 but certainly, by their falling off in groups, may also occur in 

 band-like streaks. Wedl speaks of a band-like streak, and 

 inquires whether it is not a structureless laj'er. In my 

 opinion this streak is nothing but an optical phenomenon, caused 



