ANKYLOSTOMA DUODENALE 329 



similar disease (anaemia), and ankylostoma has likewise been demonstrated 

 to be the cause of this disorder. For the last twenty years the parasite 

 has been frequently observed in Germany in brickmakers as well as in 

 miners ; it has principally been imported by Italians labouring in brick 

 works or mines ; but it also occurs amongst German labourers. It has 

 appeared most frequently in brick-fields in Bonn, and Cologne ; cases, 

 moreover, are known from the neighbourhoods of Wiirzburg, Cohsen, 

 Sollingen (near Rastatt), and Berlin. Amongst mining districts the Ruhr 

 region is most particularly liable ; as an example, during a period of one 

 year and nine months 215 cases came under observation in the Elisabeth 

 Hospital in Bochum. Similar conditions prevail in Austria and Hungary 

 (Kremnitz, Schemnitz, Funfkirchen, &c.). Belgium and France have likewise 

 yielded cases, and in Italy the worm appears to be distributed to a fairly 

 equal (and frequent) degree. 



Development. The thin-shelled eggs are deposited in a state of 

 segmentation and reach the open with the faeces ; if the atmos- 



FIG. 214. Cephalic extremity of , . , , . 



Ankylostoma duodenale, with the oral *"> 7 2I 5- ~ Ovum of Ankylostoma 



capsule. (Magnified.) duodenale. (After Parona and Grassi.)! 



pheric temperature is sufficiently high (2025 C.), they develop, 

 preferably within the excrement (but never in pure water), into a 

 rhabditiform larva measuring 0*21 mm. in length, which under 

 certain conditions may hatch out at the end of the first day, 

 and at -any rate always in the course of the second or third day. 1 

 The larvae in a few days grow to 0-560-6 mm. and moult ; 

 soon a second moult takes place, during which the oesophagus 

 changes. Nevertheless the creatures do not slip out of their old 

 larval integument. They remain actively motile, and now are no 

 longer sensitive to water, in which they may be kept alive for 

 three months ; they can also withstand a certain degree of 

 desiccation. 



1 The development also depends on the concentration and condition of the faeces ; 

 many eggs soon die off in fluid and malodorous faeces ; the addition of a 1 

 retards the development, as does the lack of oxygen and lowering of the temperati 

 The ova die without exception after twenty-four to forty-eight hours at i U 



