110 ENTOZOA. 



days may have elapsed since the worm-feeding took place ; but if 

 a microscopic examination of the rabbit's blood (from the great 

 portal and other abdominal veins) be made only twenty-four hours 

 after the time of administration, the fluid will be found to contain 

 a great number of minute cestode embryos. On further examina- 

 tion these minute hsematozoa will be found to be armed with 

 hooks for boring, and to correspond in size with the ova of T. 

 serrata, constituting the so-caUed six-hooked brood of this tape- 

 worm. About the fourth day small, white, semitransparent 

 vesicles, averaging the io of an inch in diameter, make their 

 appearance in the liver, each of them containing within its 

 interior a little embryo, measuring about the ^ of an inch in 

 length. These embryos are the same as those detected in the 

 blood, and though not actually seen in the act of migrating, have 

 evidently bored their way through the walls of the vessels into the 

 cell-tissue of the organ. At the fifth day the size of the vesicles 

 has sensibly increased (^o inch), and they now display an oval 

 figure ; their growth becomes exceedingly rapid, and by the 

 sixth day they measure the ^ of an inch longitudinally. This 

 growth continues to advance, so that at the commencement of 

 the second week, i.e., eight days after the worm-feeding, the hver 

 of the rabbit presents a more or less uniformly spotted appearance, 

 conspicuously visible to the naked eye. 



At the beginning of the third week — supposing one of our 

 experimental animals to have been destroyed at this period — the 

 liver spots are found to be considerably enlarged, especially length- 

 wise, one end of the cyst becoming narrow and pointed whilst the 

 other is still rounded. Later, in the third week, this elongation 

 becomes more striking, most of the vesicles also displaying curves 

 and undulations, which become so extended that the cysts by and 

 by acquire the form of long channels. At the fourth week many 

 of them will be found to have run into one another, producing 

 here and there a more or less regularly -branched appearance. 



All these phenomena, as they occur in tlie liver, arc iiudoubtedly 



