CESTODA 



their mode of formation, to the kind of host in which they are 

 present, and to the character of the organs in which they happen 

 to take up their residence. The so-called exogenous type 

 occurs sparingly in man, whilst the endogenous type is very 

 abundant. The peculiar form known as the multilocular echino- 

 coccus is probably a mere variety of the exogenous type. The 

 exogenous and endogenous hydatids may coexist in the same 

 bearer. In the lower animals we commonly find the organs of 

 the body occupied by numerous lobulated cysts, varying in size 

 from a walnut to a goose's egg, but sometimes rather larger. 

 They are rarely solitary, being particularly liable to occupy both 

 the liver and lungs in the same animal. The viscera are some- 

 times crowded with cysts. The hydatids do not usually protrude 

 much beyond the surface of the infested organ, but lie imbedded 

 within its parenchymatous substance. 



The multilocular variety was first described by Yirchow. In 

 reference to it Leuckart writes as follows : 



' ' Hitherto we know this growth only from the liver, in which 

 it forms a firm, solid, and tolerably rounded mass of the size of 

 the fist or even of a child's head. At first sight it looks more 

 like a pseudoplasm than a living animal parasite. If you cut 

 through the tumour, you recognise in its interior numerous 

 small caverns, mostly of irregular shape, and separated from 

 one another by bundles of connective tissue, more or less thick, 

 and including a tolerably transparent jelly-like substance. In 

 the intervening stroma a blood-vessel or a collapsed bile-duct 

 runs here and there ; but there is nowhere any trace of true liver 

 substance. The outer boundaries of the tumour are in most 

 cases pretty well defined, so that the attempt to cut these 

 growths out is not difficult. In particular spots, especially at 

 the surface, one sometimes sees white, moniliform, jointed lines 

 passing off from the tumour, and even thicker terminations 

 which, perhaps, expand in the neighbouring liver-paren chyme 

 into new (multilocular) groups of different size. In one case, 

 recorded by Virchow, the growth extended, together with 

 Glisson's capsule, a long way towards the intestine." To this 

 description it may be added, that the growth on section pre- 

 sents an appearance not altogether unlike alveolar colloid, 

 having, in point of fact, been confounded with that pathological 

 product, with which, however, as stated by Virchow, it 

 nothing in common. This is proved not only by the o 

 of the pathological features above mentioned, but also, more 



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