THE CONNECTIVE-TISSUE CAPSULE. 359 



Where the bladder-worm lies in parenchymatous organs rich in 

 connective tissue, it never leaves its cuticle exposed. It is constantly 

 found enclosed in a connective-tissue envelope, which belongs not of 

 course to the worm, but to the host and the organ inhabited. The 

 inner surface of the capsule is smooth, like a serous membrane, and 

 is furnished with a cellular layer, which is possibly of importance in 

 the excretion of the nutritive fluid. We cannot, however, regard the 

 cyst as essential to the nourishment of the animal, since it is wanting 

 in many situations e.g., in the eye and in the brain. The surface of 

 the Coenurus-c&vity (in the brain of the sheep afflicted with staggers) 

 is covered with a tough layer, which is sometimes separable in large 

 shreds, but does not exhibit in any way the ordinary structure of the 

 bladder-worm cyst. One can indeed see in it the remains of nervous 

 substance and vessels in all stages of disintegration and degeneration, 

 a striking proof of the disastrous effect of parasites. 



The connective-tissue cyst of the adult bladder- worm is by no means 

 always identical with that which surrounds the young parasites after 

 their immigration. It only persists when the worm remains in its 

 first resting-place. But occasionally the worm retains for some time 

 the power of changing its abode, especially if the organ in which it 

 has landed is poor in connective substance. In spite of their increased 

 size, the young immigrants press slowly forwards, probably by con- 

 tinuous peristalsis, and press the surrounding tissue to the side. Thus 

 one finds young Ocenuri on the surface of the brain, forming passages 

 an inch long, lined with long shreds of exuded matter. Similarly 



FIG. 206. Brain of a lamb with passages of Coenurus (natural size). 



the Cysticerci of the liver and lungs press ever outwards, and often 

 break through into the body-cavity. There are even species which reach 

 the body-cavity in this way only. To these belongs, for instance, the 

 Cysticercus pisiformis, so common in our hares and rabbits. Three 

 or four weeks after an infection with Tcenia serrata, the liver of 

 these animals is seen to be perforated often by countless white 

 streaks the borings of the young Cysticerci which almost all 

 gradually lead to the surface, and allow their inmates to get out. 



