630 VARIOUS FORMS OF ECHINOCOCCUS. 



though the inhabitants had originated within it. The resemblance of 

 this to the primary Echinococcus cavity is all the more striking, since 

 the inner surface of the alveolus is covered with the same irregularly 

 formed granular cells which we have already described. Between 

 these one finds numerous fatty granules, haematoidin crystals, and 

 clot-like structures, which become more abundant the nearer one 

 approaches the ulcerated parts. Nor is there any lack of bile-pigment 

 and salts of lime. The latter sometimes impregnate the wall of the 

 cavity so abundantly (as is occasionally observed in other bladder- 

 worms), that they may be extracted from the alveolus in the form of 

 a more or less continuous shell. The intervening connective tissue 

 also often becomes the seat of a calcareous deposit, in which localities 

 the structure of the connective tissue is gradually destroyed. The 

 fibrils disappear, the fundamental substance becomes turbid and 

 granular, until the alveolar wall is ultimately changed into a caseous 

 mass, the destruction of which is followed by ulceration and formation 

 of lacunae. 



If it were necessary to corroborate the parasitic nature of the so- 

 called "alveolar colloids" by further facts, we might refer to the 

 chemical character of the bladder-walls, which exactly correspond to 

 the cuticular membranes of the usual Echinococcus- bladders, of which 

 they are also the histological equivalents. We have already learned 

 from Frerichs the essential chemical properties of this substance, and 

 have seen that it belongs neither to the proteids nor to the gelatinous 

 tissues. The recent and minute investigations of Liicke l have con- 

 firmed these statements, and have proved that the cuticle of the 

 Echinococcus is chitinous, although it differs from the usual Arthropod 

 chitin in possessing less power of resistance against caustic alkalies and 

 boiling water. There are, however, many differences between the 

 older and younger JEchinococcus-\)la.ddeTS, not only in their behaviour 

 towards 1 reagents, but also in their elementary composition, 2 and in 

 the analysis of their ash. 3 By the proper application of sulphuric 

 acid and hot water, the cuticle of the Echinococcus, like ordinary 

 chitin, may be partly changed into grape-sugar, although the amount 



1 Archivf. palhol. Anat., Bd. xix., p. 189, 1860. 



2 The results of Liicke's analyses are : 



Old Bladders. Young Bladders. 

 Carbon = 45 "342 44-068 



Hydrogen = 6 '544 6707 



Nitrogen = 5 "1493 4 '478 



Oxygen = 42 "9547 44747 



3 This difference in the ash (young bladders = 1579 per cent., old bladders only = 0'28), 

 which consists principally of salts of lime, is so striking, that we feel inclined to ask whether 

 the membranes were in both cases equally freed from the inner parenchyma and from 

 the calcareous corpuscles ; but of this Liicke does not inform us. 



