WANDERINGS OF THE EMBEYOS. 339 



stages found, according to circumstanees, in the naost diverse organs, 

 now in the liver or in the lungs, now in the muscles or in the connec- 

 tive tissue, and even in the brain and eye. It is, however, generally 

 the liver which is temporarily or permanently inhabited by cystic 

 worms. 



Kiichenmeister has tried to explain this special preference for the 

 hver ^ by supposing that the six-hooked brood, after becoming free, 

 seek out the bile-duct, and thus pass directly into the liver, but there 

 is no warrant for this supposition. I have examined perhaps a dozen 

 rabbits in the course of the first day or two after infection, and I never 

 found the embryos in the bile-ducts, though their presence there could 

 have been detected without much difficulty. On the other hand, I 

 have several times succeeded in finding unchanged embryos in the 

 portal vein, and have thus proved that at least some of the wandering 

 embryos get into the venous system, and are carried through their host 

 by the blood-stream.^ With this agrees Leisering's^ statement that in 

 the case of a lamb which was fed with Tcenia ynarginata, and died five 

 days after with symptoms of icterus, he found " hundreds " of small 

 " point-like " worms in the much enlarged network of the portal vein. 

 These could be nothing but the further development of the young 

 brood, although the embryos of T. serrata would, as we shall see, by 

 that time have reached and become encapsuled in the liver. It is 

 therefore natural to connect the frequent occurrence of cystic worms 

 in the liver with their wanderings into the blood-vessels, since the 

 capillary network in the liver is the first at which the embryos would 

 arrive, and since the size of the latter (on an average about 0'022- 

 0'028 mm.) hardly admits of a free passage. 



It is, of course, still a moot-point whether this is the only way 

 which the embryos can successfully pursue. This much at least is 

 certain, that there are tape-worms which do not spend their youth in 

 the hver with anything like the same constancy as Tcenia serrata and 

 T. marginata, but are indeed found far more frequently in other 

 organs, such as the muscles or brain. Judging from the mode of dis- 



has actuaUy found the embryos of Twnia crassicollis in the intestinal wall of the mouse. 

 It was especially the middle portion of the small intestine where the embryos were seen in 

 the free condition, and sometimes in such numbers that ten could be counted in one field 

 of the microscope. — R. L.]. 



' So at least in the first edition of his work on parasites. Afterwards, in the second 

 edition (p. 52), he supposes that the parasites are carried throughout the body by the 

 blood and lymphatic Tessels, especially by the latter. 



^ [In agreement with this, Raum (loo. cit., p. 30) has found six-hooked embryos of 

 Twnia crassicollis in blood from the portal vein of mice, into which they had been intro- 

 duced nine, twenty-seven, and fifty-two hours previously ; as also in the capillaries of the 

 liver, where their further development could also be studied. The bile-duct was free from 

 embryos. — R. L.] 



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