DIAGNOSIS OF PARASITIC DISEASES. 145 



case is reported by O'Neill ^ from the West Coast of Africa, where a 

 skin disease resembling itch occurs among the negroes, and is also 

 attributed to the presence of young Nematodes. I have myself had 

 the opportunity of confirming the existence of such parasites on the 

 skin of a diseased fox, but am still doubtful whether the disease can 

 be called parasitic; and I have been confirmed in this doubt by 

 finding, among the scabs of the eczematous skin of a dog, numerous 

 flea-larvse, which could hardly have produced the eruption, but had 

 probably only taken advantage of it as an abundant source of food. 



Glancing over the various pathological states induced in manifold 

 ways by our unbidden guests, we survey a long catalogue of affections 

 of most varied nature and importance. It is but rarely, however, 

 that they show a combination of features so specific and characteristic 

 that one can at once and with probability decide as to their nature 

 and etiology. On the contrary, the results of parasitism might, in the 

 majority of cases, be referred quite as well to entirely different 

 causes. 



DIAGNOSIS. 



Such being the case, it is evident that a sure diagnosis of helminthic 

 diseases necessitates, in the majority of cases, an objective proof of tlie 

 existence of the parasites. 



This proof may be furnished in various ways, according to the oc- 

 currence and nature of the parasites. It is most readily forthcoming, 

 if we omit the Epizoa from consideration, in the case of those which 

 inhabit the alimentary canal, or other organs opening to the exterior, 

 not only because the animals frequently pass out of themselves, or are 

 expelled by proper treatment, but also because, with few exceptions, 

 they are sexually mature, and produce eggs in such immense quan- 

 tities that their detection in the excreta by the aid of the microscope 

 is a matter of very little difficulty. The importance of the examina- 

 tion of human excrement has been already emphasised on all hands, 

 especially by Davaine,^ Lambl,* and Vix,* and even earlier by 

 Malmsten and others. 



Among the Helminths infesting man there are (including Bochmius) 

 nine species which have to be considered in such examinations : — • 



Three Cestodes — 



Tcenia saginata (Fig. 90, H). 



„ solium (/). 

 Bothriocephalus latus {K). 



' Lancet, Feb. 1878. " Prager Vierteljakrsachrift, Bd. i., p. 1, 1859. 



* M(m, soc. iiol., t. iv., p. 188, 1857. * AUgemeine Zeitschr. f. Psychiatrie, p. 114, 18C0. 



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