144 PKACTICAL PAEASITOLOGY 



Europe. They are Tcenia saginata, T. solium, and Dibothriocephalus 

 latus. The last-named is found in certain districts only, where it 

 is also parasitic in the dog, the cat, and the fox. The two Tsenia 

 varieties are confined solely to man and they may be extra-European 

 in their occurrence. To these three species Hymenolepis nana must 

 be added; it is native to the districts bordering the Mediterranean, 

 though it is also met with farther north. It is a specific parasite of 

 man. All other European tapeworms, and probably also those which 

 occur outside Europe, are only occasional habitants of man, their 

 normal hosts being mammalians of other genera and in one (doubtful ?) 

 case, of birds. To these belong Dipylidium caninum of dogs and cats ; 

 H. diminuta of rats and mice, which has been encountered only in the 

 South of Europe and outside it ; and H. lanceolata of geese and other 

 fowl, which was upon one occasion found in a man at Breslau. Man 

 may also harbour the Cysticercoid stages of certain worms. To some 

 of these he is also the definitive host (T. solium, T. saginata) ; others, 

 again, only attain maturity in other mammalians (T. echinococcus of 

 dogs) ; while, in a certain proportion of cases, encountered only in 

 Eastern Asia, both the adult parasite and the host which harbours 

 it, are unknown. 



The varieties most easily obtainable in Central Europe are : 

 T. saginata of man ; Dipylidium caninum of dogs and cats ; 

 H. diminuta of rats and mice ; and H. lanceolata of geese. T. solium, 

 which was formerly very prevalent in Northern Germany, has now 

 become scarce, 1 while Dibothriocephalus latus is very limited in its 

 distribution, being found only in the coast districts of Northern 

 Germany (especially towards the east), in the neighbourhood around 

 Starnberg, and in Switzerland. Of the Cysticercoids observed in man, 

 those most easily obtainable are : Cysticercus cellulosa, of the T. solium 

 of swine ; C. bovis, of the T. saginata of cattle ; and Echinococcus 

 veterinorum, of the T. echinococcus of cattle, swine and sheep. 



Cestodes should be examined as follows : A whole worm should be 

 washed in tepid normal saline and then put into a shallow glass vessel 

 of sufficient size, together with clean normal saline, and placed upon 

 a dark background. Preserved specimens are taken out of the vessels 

 in which they have been stored and are put, with the preserving fluid, 

 into shallow bowls or on to plates. The worm will be found to consist 

 of a varying number of segments or proglottides, which increase in size 

 and alter in shape towards the posterior end. At the anterior end is 



1 A good substitute for demonstration purposes is T. crassicollis of cats or, better 

 still, one of the larger varieties (T. marginata, T. serrata, T. coenurus) from dogs. 

 Cestodes which have been expelled by means of anthelminthics from man, are 

 usually useless for histological purposes. 



