ZOOLOGY. 361 



soon to he executed, and, as was to be expected, with perfect success. Measles 

 taken from fresh pork, and put into sausages which the criminal ate raw, at 

 certain intervals before his death, were found again, in the post-mortem 

 examination, as tapeworms in his intestine, and in different stages of devel- 

 opment, according to the intervals in which the measles had been taken. 



Thus it became clear that all hydatids are tapeworm larva;, which, when 

 swallowed with the animal, or a portion of it, in which they live, by another 

 animal, develop in the intestine of the latter. 



Now the opportunity for experiments was again open in another direction. 

 If the tapeworm embryo developed its scolex or head by interior budding, it 

 was likely that those animals having hydatids got them by eating the eggs 

 of the species of tapeworm to which those hydatids belonged. And this has 

 been proved by experiment. Goats fed with eggs of the Tcenia Echinococcus 

 got the Echinococcus; sheep fed with the eggs of Tcenia Coenurus got the 

 Coenurus in their brain; healthy young hogs fed with the eggs of the human 

 tapeworm got the measles. Kiichenmeister, Siebold Van Beneden, Gurlt, 

 Luschka, Wagener, Leuckart, Eschricht, and others, have the merit of trac- 

 ing this interesting development. From their further investigation, it became 

 moreover evident that the Ccenurus also, with its many heads, originated 

 from one embryo, which, enlarging greatly, throws out as buds from its inte- 

 rior, not one, but many scolices ; moreover, that the process is also exactly 

 the same in Echinococcus, except that in this hydatid the scolices free them- 

 selves after a while from the internal walls of the bladder, and thus swim in 

 the fluid contained in the bladder, the latter itself being simply the enlarged 

 embryo. 



But the zeal of these investigators did not rest here. If the sheep gets by 

 chance the eggs of the Tcenia Coenurus of the dog into its stomach, how do 

 the embryos hatching from those eggs reach a suitable place for their devel- 

 opment into hydatids, which place is, in the sheep, the brain? It had been 

 erroneously assumed that they bored with their spines recta via from the 

 stomach through all the tissues and organs until they reached the brain. 

 Accordingly, in the hog, the embryos of the Tasnia would have to go from 

 the stomach into the muscles; in the rat, into the liver; and in the ox, into the 

 lungs; for it is only in these particular organs that these hydatids are found. 

 R. Leuckart, however, discovered the way in which the embryos actually 

 reach their destined resting places. On feeding rabbits with the eggs of 

 Tcenia serrata, he found that, some hours after the feeding, the egg-shells 

 were already dissolved into prismatic granules by the juices of the stomach, 

 and the embryos set free. But on putting the eggs immediately in the 

 intestine (through an artificial opening) they were not hatched. It was clear, 

 therefore, that only the gastric juice could hatch the embryos; and this 

 accounts at once for the strange fact, that the embryo never hatches in the 

 intestine of the animal where the tapeworm itself lives. Moreover, he found 

 that they do not pass from the stomach into the intestine, and hence, as had 

 been supposed, through the bile-ducts into the liver, but that they pierce the 

 blood-vessels, and thus come into the circulation. He even, after a long search, 

 found four perfect embryos in the blood taken from the vena portai. It is by 

 the blood that the embryos of tapeworms are carried to the organs in which 

 they develop into hydatids. It now at once became obvious how easily they 

 reach the muscles, the brain, the lungs, etc. But it is to be supposed that 

 only those which reach the destined organ will develop themselves, while the 

 rest, which are carried to other organs, must perish. 



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