CYSTICEKCUS TENUICOLLIS. 189 



sygdan/ by Eschricht, separately printed from the ' Bibliotliek 

 for Laeger/ January, 1854-, and Schleissner's ' Nosographie 

 Islands/ 



3. ECHINOCOCCI. 



The Echinococci have long furnished a point of dispute for 

 helminthologists. Some only admit a single species of Echino- 

 coccus ; others two; and others that there is a still greater num- 

 ber of species, such as Leuckart, who regards an Echinococcus of 

 the camel and that of the peacock as distinct from the other 

 species. The Echinococci are usually divided (and amongst 

 others even by Yon Siebold) into Echinococcus hominis and E. 

 veterinorum. This is incorrect, for Haubner and Creplin have 

 ascertained the occurrence of Echinococcus hominis in cattle, and, 

 on the other hand, Von Ammon has found E. veterinorum in 

 the human eye ; and from Eschricht's description of the Echino- 

 coccal disease in Iceland, it appears also, that in that island, 

 both species occur in the human subject. That the latter two 

 species are really distinct, further proofs will be furnished in the 

 following remarks. We shall pass over here the differences by 

 which the Echinococci are distinguished from the Cysticerci and 

 Cwnuri, and only mention in passing that the Echinococcus- 

 cyst proliferates almost throughout its whole extent, and that 

 we cannot speak of it as a caudal vesicle ; that the Echinococcus- 

 cyst is firmly attached to the enveloping cyst ; that the walls 

 are composed of lamellae ; that no muscular layer follows upon 

 this stratified membrane, as in the Cysticerci, but that it is imme- 

 diately followed by a layer of a gran ulo- vesicular structure, with a 

 vascular system and calcareous corpuscles. All these points 

 will be referred to in detail hereafter. But the differences in 

 the developmental history of the two species will be more ex- 

 actly detailed. From the internal vascular layer of the Echino- 

 coccws-vesicle, spring small buds, which, forming conical or 

 villus-like elevations, sometimes measuring 0*4 mill., become con- 

 verted directly into Jte^a-heads, in the formation of which 

 there is not usualty an immediate conversion of the processes 

 into heads ; but first of all a transformation of the processes 

 into small brood-capsules, 0*7 2 mill, in diameter, and it 

 is only in these that the scolices are produced or budded 

 forth. The process, which at first adheres by a tolerably broad 

 base, becomes in this way cleared, its contents more fluid, 



