328 PARASITES OF MAN. 



Larvfo. — Although the history of the development of the young 

 worms has not actually been ascertained, it is tolerably certain 

 that the structural characters they exhibit, and the changes 

 they undergo, are similar to those of other closely allied species. 

 Thus, without doubt, the free embryos are rhaVjditiform, and 

 pass their larval lifetime in water, mud, and moist earth. 

 After having undei'gone one or more changes of skin, attended 

 with growth, they are possibly transferred to the human 

 stomach. 



Intermediate host. — It is not certain that any intermediai-y bearer 

 is necessai-y. 



Eemarks. — Water drinkers in tropical climates readily become the 

 victims of this parasite, either by swallowing the free swimming 

 larvje, or water insects containing the larvte in a state of rest. 

 The Dochinius duodenalis was discovered by Dubiui, at Milan, in 



. 1838, and its clinical importance in relation to the so-called 

 Egyptian chlorosis was first announced by Griesinger. We now 

 know that this destructive little parasite is a fertile cause of the 

 wasting disorders of tropical countries generally ; the aiifections 

 termed tropical anarnia or hypoixmia being especially prevalent in 

 the West Indies, in Cayenne, in Bi-azil, in Egypt, and in the 

 Comoreu Islands lying to the north-east of Madagascar. The 

 worms are veritable bloodsuckers, beha^nng like leeches ; 

 probably, however, the loss of strength and diminution of vital 

 power which they occasion is not so much due to the actual 

 amount of blood abstracted as to the severe irritation resulting 

 from the injuries they inflict upon the mucous membi'ane of the 

 infested intestine. 



Lit. — The Work of Leuckart ; and especially a Memoir by Wucherer 

 in Deutsches Archiv fur E^inische Medicin, Sept. 27, 1872, 

 (s. 379—400.) 



fTO BE CONTINUED.] 



ON THE MICROSCOPICAL EXAMINATION OF CLAY. 



BY THK REV, H. W. CROSSKEY, F.G.S. 



A brief record of the results of considerable practical experience in 

 the microscopical examination of clay may be of service to those engaged 

 in the study of the drift beds of this district. As an illustration of what 

 may be done by the employment of a good method, it may be mentioned 

 that when the vvriter, in conjunction with his friend, Mr. D. Robertson, 

 commenced to deal microscopically with the glacial clays, only two 

 doubtful species of Ostracoda had been observed as fossils in them. We 

 have succeeded, however, in cataloguing 136 species, of which 19 are either 

 now extinct or unknown in the living state, and many are of extreme 

 rarity.* 



The first essential point is tJwrottgJtbj to dry the clay. This ought to 

 be slowly done. The clay should not be placed in an oven or close to a 



* See Monograph on the Post Tertiary Entomostraca of Scotland, by G. R. 

 Brady, Bev. H. W. Croeskey, and D. RobcrtBon. Published by the Palseontographical 

 Society, 1874. 



