136 THE EFFECTS OF PARASITES OX THEIR HOSTS. 



third or fourth week after they have been administered to the animal, 

 the passages which they have made close up. The former congested 

 condition then ceases, the exuded material which, along with the 

 worms, had blocked the passages is reabsorbed, and a healthy appear- 

 ance returns. Only the persisting scars betray the former state of the 

 organ. 



I have found it to be the same in the case of Cysticercus tenui- 

 collis, except that, as this is of larger size at the time of its exit, it may 

 under similar circumstances produce more serious effects. In livers 



FIG. 83. Exit of a young 

 Cyaticercua tenuiroUis from the 

 liver. 



FIG. 82. A piece of the liver of the rabbit with 

 perforations caused by bladder- worm (Cysticercu* 

 pisiformi*). 



which had just been left by these parasites, I have seen holes so long 

 that the finger could be inserted nearly half-an-inch. The healthy 

 state of my animals is explained by the fact that the number of para- 

 sites was not very large, never indeed above twelve. The emigration 

 of a greater number produces not seldom, however, fatal effects. 



Much more dangerous are the consequences of the repeated wander- 

 ings of Pentostomum denticulatum (see p. 77) from the liver and lungs. 

 In order to understand this, it is only necessary to see the rapid and 

 powerful leech-like motions of the animal and its armature, consisting of 

 circles of hard bristles and the powerful hooks (Fig. 56). After a 

 copious infection, the liver and lungs are perforated in all directions, 

 and their surfaces are covered with holes (Fig. 84), each of which 

 forms the centre of a more or less extensive inflammatory circle. 

 This is especially the case in the lungs, which are often greatly dis- 

 tended by infiltration of blood and exuded fluids. When the Penta- 

 stoma migrate in larger numbers into the cavity of the body, these 

 symptoms are usually accompanied by peritonitis, which frequently 

 terminates fatally. x Even cases of natural infection may be followed 

 by fatal results, as is proved by the instance which Weinland gives of 



A Leuckart, "Bau und Entwicklungsgesch. von Pentastomum tsenioides," p. 14, 

 Leipzig, 1865. 



