FORMATION OF THE YOUNG BLADDERS. 501 



surrounded by connective tissue ; for, strictly speaking, the muscular 

 bladder-worms inhabit the inter-muscular connective tissue, but this 

 connective substance is scarcely more strongly developed than usual, 

 and is so far from forming a true cyst, that the bladder-worms fall 

 out immediately when the bundles are separated. The only pecu- 

 liarity of the surrounding connective tissue is the presence of a finely 

 granular substance, which lies next the bladder, and, on closer exami- 

 nation, is seen to be composed of membraneless cells, which enclose a 

 clear nucleus (0*007 mm.), and are so indistinctly marked off from one 

 another that the irregular processes of the borders seem to flow into 

 one another. 



But the bladders were not all of this small size. The great majority 

 were considerably larger between 3 and 4 mm. some had even 

 grown to 6 mm. These differences seem so striking, that I can well 

 believe that the smallest bladder-worms had been retarded in their 

 development, and represented a stage which one would look for about 

 the twenty-fourth day. 



With the increase in size, the surrounding connective-tissue mass 

 has also gradually attained a more marked development, so that, espe- 

 cially in the larger bladder- worms, one can justly speak of a special, 

 though still delicate, capsule. The form of the bladder has also 

 changed, inasmuch as the long diameter with which the course of the 

 fibres corresponds is now at right angles to the axis of the head, and 

 is in some so much increased, that it bears to the transverse axis the 

 ratio of 6 to 2 '5. It is probably, however, only the pressure of the 

 muscles that alters the original spherical form in this way. 1 Similarly 

 we must refer the constantly lateral position of 

 the head-rudiment to the fact that the lateral 

 surfaces of the bladder stand in closer connection 

 with the blood-vessels surrounding the muscular 

 fibres than do the terminal parts. The former 

 have therefore more advantageous conditions 

 of nutrition. 



The Organization of these bladder-worms is , Fl , G - W*>Cy*ticcrcu 



, , . . .. celiulosce with the forma- 



already quite complete, general size and head- tion of the head just 

 structure excepted. Even the smallest are be g innin g- (xio.) 

 vesicles enclosing a clear, non-granular fluid, and exhibiting in their 

 walls a distinct and abundant vascular system, with ciliary lappets 



1 I may mention that I once found two muscle bladder-worms in the same cyst, in 

 which the bladder-body was elongated only at the free outer ends, while the other segments 

 exhibited a simple semi-crescentic structure. Even the older helminthologists have noted 

 the occurrence of two bladder-worms in the same capsule. See the collection of these 

 cases by Stich, Ann. des Charitt-Krankenhauses, p. 169: Berlin, 1854. 



