156 WORMS INFESTING THE DOG. 



developed, is capable of separating itself, and progressing by its 

 own vermicular motion for any reasonable distance, containing 

 within itself a mass of eggs, which are only hatched in the 

 stomach of the rabbit, sheep, or other herbivorous animal after the 

 integument is digested and they are thereby set free. This tape- 

 worm often attains a length of many feet, and may readily be 

 distinguished by the square form of its joints from the T. cucu- 

 merina, whose joints are oval, and exactly resemble the seeds of 

 the cucumber, from which it derives its specific name. It appears 

 to be clearly ascertained from careful observation, that when this 

 tape-worm is mature, segments (proglottides) are continually 

 given off, which may be considered as distinct animals, or perhaps 

 it would be more correct to describe them as being ovarian bags, 

 provided with muscles for locomotion. By this means they are 

 able to leave the mass of faeces with which they have been passed 

 out of the rectum of the dog, and creep away to the nearest grass, 

 where they either die from being dried up, or they are swallowed, 

 in contact with its food, by some rabbit, hare, sheep, or other 

 ruminant. In the stomach of either of these animals the envelope 

 is digested, and the eggs are set free, each of which is soon 

 hatched, and by its boring powers reaches the blood-vessels, 

 through which it is transmitted to its proper seat. It is most 

 probable, though this fact is not yet demonstrated, that these ova 

 in the hare and rabbit are developed into, the cestoid-worm, 

 known as Cysticercus pisiformis, which is found very commonly 

 attached to the viscera of the rabbit and hare in the form of small 

 globular vesicles or cysts. Again, when they are developed in 



