514 THE ANIMAL PARASITES OF MAN 



If the views of Loos are correct, the prophylactic measures are plainly 

 indicated. In the infected countries energetic measures must be taken to 

 prevent the urine of infected individuals from ever reaching the rivers. The 

 embryos will soon perish in closed sewers. The greatest precautions are neces- 

 sary in regard to bathing, especially in the neighborhood of habitations in 

 which infected persons are living. 



A therapy directed to the expulsion of the worms will probably always 

 remain useless. Efforts to expel them by turpentine oil or extractum filicis 

 maris have been, according to the reports of Brock, unsuccessful. We are, 

 therefore, entirely restricted to symptomatic treatment. 



I may mention another trematode, the 



Monostomum lentis of Nordmann, 1833, 

 which was once found in an extracted lens; this form is probably identical 

 with the distomum oculi, Ammon, 1833. 



Hexathyridium pinguicola, Treutler, 1793, and hexathyridium venarum 

 are also counted among the trematodes. 



CESTODES 



Cestodes, tape-worms, have been known from antiquity as parasites of 

 man. Following the definition of Leuckart, we understand by cestodes flat- 

 worms without mouth or intestine, which develop by generation and by gem- 

 mation upon a scolex, and remain united for some length of time in a ribbon- 

 like colony. 



The scolex, known under the name "head of the tape-worm," is supplied 

 with two to four suctorial discs, and generally also with hooks that are bent 

 like a claw. 



The head serves as the adhesion apparatus. The flat, two-edged links of 

 the chain (proglottides) grow away from the point of junction. The smallest 

 links contain the ova in which develop the embryos (oncospheres), which in 

 the bothriocephali are ciliated. Only these, reaching the outside world, per- 

 forate the shell of the ovum, and swarm in the water until they finally reach 

 an intermediary host. The ova of the other cestodes emerge into the outside 

 world with the feces, or still enclosed in the proglottid, and are at last taken 

 up by a suitable host. The oncospheres, enclosed in small cysts or embedded 

 in closed cavities of the body, develop in the host into scolices which, subse- 

 quently, are taken up by the actual host and grow into tape-worms. 



The best-known of the tape-worms parasitic in man are the tenia solium, 

 Eudolphi, 1810, and the tenia saginata, Goeze, 1782. 



I may forego a detailed description of these two parasites, since they are 

 well known. I shall only briefly outline their differentio-diagnostic charac- 

 teristics. 



Tenia solium is distinguished by a head which is supplied with a rostellum, 

 a double row of booklets and four suctorial discs. The proglottides, number- 

 ing 800 to 900, contain the testicles and the easily recognizable uterus con- 

 sistmg of a medial trunk and of seven to ten. lateral branches upon either 

 side. The marginal sexual papills alternate quite regularly. The rounded 



