116 



PARASITES OF MAN 



particularly, by the well-ascertained presence of echinococcus- 

 heads in most of the so-called alveoli. Several hypotheses 

 have been broached with the view of explaining the mode in 

 which these multilocular hydatid growths are formed. Virchow 

 thought that the echinococcus vesicles were primarily formed in 

 the lymphatic vessels, whilst Schroder van der Kolk supposed 

 that they originally took up their abode in the biliary ducts. 

 Although, thanks to the courtesy of Professor Arnold Heller in 

 giving me a specimen, I have been enabled to confirm much that 

 has been written in respect of the morbid appearances, I can 

 add nothing towards the solution of the difficulty in question. 

 Until lately it was supposed that the multilocular variety of 

 hydatids only existed in man, but Professor Bellinger has 

 encountered it in the liver of a calf. 



Selecting any ordinary fresh example of the exogenous kind, 

 and laying the tumour open with a scalpel, we notice in the 



first instance an escape 

 of a clear transparent, 

 amber -coloured fluid. 

 This previously caused 

 the distension of the 

 sac. If the tumour is 

 large, this escape will 

 probably be followed 

 by a falling in, as it 

 were, of the gelatiniforin 

 hydatid membrane, in 

 which case the inner wall 

 of the external adventi- 

 tious investment or true 

 fibrous cyst will be laid 

 bare. If the hydatid be 

 next withdrawn from the 

 cyst, it will be seen to 

 display a peculiar tremu- 

 lous motion, at the same 

 time coiling upon itself 

 wherever there is a free- 

 cut margin. Further 

 examination of portions 



FIG. 30. Ectocyst, endocyst, and brood capsule of Echinococcus. 



*'roiu a Zebra, After Huxley. OI the hydatid will show 



that we have two distinct 



