612 VARIOUS FORMS OF ECHINOCOCCUS. 



they bud forth. But as the twigs are morphologically nothing more 

 than repetitions of the stem from which they spring, so are the brood- 

 capsules, in a certain sense, nothing more than repetitions of the 

 bladder which bears them. They are daughter-bladders, individually 

 developed members of the Echinococcus, through whose budding the 

 originally simple bladder-worm forms a colony. Although morpho- 

 logically equivalent to the mother-bladder, they attain only an imper- 

 fect physiological individuality, as is so frequently the case in colonies. 

 They remain connected with their mother-bladder, and undertake for 

 the latter, according to the law of the division of labour, the function 

 of head-formation. This specific function accounts for the differences 

 which we have seen to obtain anatomically between the brood-capsules 

 and the mother-bladders, and which essentially consists in the inverted 

 order of the cuticle and the parenchymal sheath. 



In many cases, especially in the Echinococcus of cattle (E. veteri- 

 norum), the worm remains in the above state till its host dies, or till 

 the heads find an opportunity of becoming Tcenice (p. 591). The 

 only change, apart from the multiplication of brood -capsules and 

 heads, consists in a continued, though perhaps but slow, growth of the 

 bladder. We know, however, instances in which the Echinococcus 

 (and that the simple form) has grown so as to attain a diameter of 

 15 cm. As a rule, indeed, the worm in this form attains but a 

 comparatively small size hardly greater than that of a fist or 

 an orange. 



In this increase in size the cuticle also participates, and that to a 

 much greater and more striking extent than the parenchymal sheath. 

 It becomes thicker the more the bladder-body grows, and in many 

 cases measures as much as 1 mm. or more. The lamellar stratification 

 remains as before, except that the lamellae become more sharply 

 defined, and increase in thickness. Nor does the elasticity of the 

 cuticle experience any diminution: it seems in the large bladders 

 hardly less conspicuous than in the small ones. One only needs to 

 touch them to see how the tremulous motion spreads over the whole 

 mass. This is not only perceptible to sight and feeling, but even to 

 hearing, so that, after the example of Brian^on and Piorry, the so-called 

 " hydatid tremor " and rustling obtained on percussion have been used 

 as a corroboratory diagnostic test. 1 



As the cuticle thickens, so does the connective-tissue cyst sur- 

 rounding the worm. It becomes a sac, the wall of which often measures 



1 See on this point besides Piorry, "De la percussion mediate," p. 153, Paris, 1828, 

 and especially Davaine, Gazette mtd., No. 20, 1862. Kiichenmeister maintained for some 

 time the erroneous opinion that this rustling noise was audible only in the hydatid form 

 of Echinococcus. 



