ECHINOCOCCI OF THE LITER. (597 



CHAPTER X. 



EC1IINOCOCCI OF THE LIVER. 



ETIOLOGY. Echinococci hold the same relation to taan la echinocoo 

 2iis (Siebold) that cysticercus cellulosae does to taenia solium ; i. e., 

 they are the young, sexless brood of the mature tape-worm. Experi- 

 ments of feeding animals with echinococci from man have given no 

 decided results, it is true ; but the tsenia echinococcus has been found 

 in the intestines of animals that had been fed on echinococci from 

 other animals. 



It is doubtful how the egg and embryo of the taenia echinococci 

 reaches the human liver, there to develop to echinococcus vesicles. 

 In Iceland they are so common, that physicians there say that one- 

 eighth of all the diseases of that island are due to this disease, and 

 that about every seventh person contains echinococci (Ifilchenmeister). 

 From analogy, it is supposed that the migration takes place as follows : 

 Animals affected with the taenia echinococcus evacuate mature links 

 from the bowels ; the eggs or embryos contained in these in some way 

 get into the drinking-water, or come in contact with some food that is 

 eaten raw. Entering the intestinal canal with these, the small em- 

 bryos with their six hooks bore into the wall of the stomach or intes- 

 tine, and, wandering farther, they finally reach the liver. There the 

 microscopic embryo swells to a large vesicle, on whose inner wall a 

 colony of young, immature taeniae or scoleces is developed. In most 

 cases, besides the scoleces, daughter vesicles develop in the mother 

 vesicle, or rather wet nurse ; in these, a second generation of vesicles 

 is formed, whose inner wall is also covered with scoleces. 



Kilchenmeister refers the endemic occurrence of echinococci in Ice 

 land principally to the number of dogs kept there, and to the warmth 

 of the river-water, which is much used for drinking. The dogs prob- 

 ably eat the vesicles that have been evacuated from the mouth, anus, 

 or suppurating sacs that have not been taken care of. The warm tem- 

 perature of the water is favorable for the embryos of the echinococcus. 

 as it is for all the lower animals. JZilchenmeister considers it as not 

 improbable that, when the echinococci reach the bowels of the person 

 in whom they exist, they there develop to taenia, and conversely that 

 the embryo escaping into the intestines of persons affected with taema 

 may become echinococci. 



ANATOMICAL APPEARANCES. Echinococcus sacs are sometimes 

 solitary, sometimes very numerous in the liver, and occur more fre- 

 quently in the right lobe than in the left. Their size varies from that 

 of a pea to that of a fist or a child's head. If they are large and 



