216 ANIMAL PAEASITES. 



Echinococci, which, however, only exhibited two parallel layers 

 (an outer one of 0-04 and an inner one of 0-0.25 millim. in thick- 

 ness). Yellow, granular, and diffused pigment, and beautiful 

 small crystals of hsematoidine, were also deposited. The sacs 

 thus closed frequently remained long in connection with the 

 processes. 



From the surface of the membrane also, small, yellowish, 

 knobbed appendages were given off, containing a cavity in the 

 knobbed extremity. 



Around and between the membranes lay in groups concentri- 

 cally stratified bodies, consisting of calcareous salts with organic 

 basal substance, measuring from 0*025 0'03 millim., held to- 

 gether by granular connective tissue. The fluid of the cavities 

 in the interior of the alveoli contained acicular, caraway -like, and 

 probably fatty crystals, and besides these the scolices of Echino- 

 coccus made their appearance both on the inner wall and free in 

 the contents of the alveoli, generally with the circlet of hooks 

 retracted, some larger (0*23 0'33 millim. in length and 0*12 

 millim. in breadth behind) with the head protruded but mostly 

 destitute of the circlet of hooks, and others hookless and so small 

 (0'12 millim. long and 0*07 millim. broad) that Virchow thinks 

 they had not attained to the formation of hooks. Their cal- 

 careous granules measured up to 0-006 millim. The hooks, un- 

 fortunately, were not measured. 



After this description, Virchow sums up his views as to this 

 structure as follows : 



"1. These tumours have nothing to do either with cancer or 

 with alveolar colloid. The distinctions from the latter consist in 

 the composition of the tumour out of isolated animals becoming 

 developed close together, in the passage of the tumour into central 

 ulceration by retrogressive metamorphosis of the animals and the 

 stroma, and in the regular progress of the animals from the 

 surface of the liver towards the intestine and porta, on which the 

 largest and fullest vesicles were placed, whilst only small and 

 collapsed vesicles occur on the surface. 



" 2. The Echinococci of the liver do not take up their abode in 

 the gall-ducts (Schroder van der Kolk), but the gelatinous masses 

 follow the portal system and form aggregations, more or less con- 

 nected, as though situated in a system of canals, close to the 

 biliary and blood-vessels. They are placed therefore in the 

 lymphatic vessels. Perhaps the great resistance of the walls 



