76 



body by scarcely any constricted ueck. The head is quadrangular, is 

 about oue-twenty-fiftli of an inch in diameter, and has a circlet of from 

 thirty-two to forty hooks at its apex, and four moderate sized suckers. 

 The specimen figured contained twenty-eight. These hooks and suck- 

 ers serve to anchor the parasite to the intestinal walls. The neck is 

 short, and at a little distance from the head shows the division into seg- 

 ments which become plainer and plainer towards the end of the body. 

 The segments are at first very short and broad, but gradually lengthen- 

 ing become square where the animal is widest when relaxed, and about 

 twice as long as broad at the end. The terminal segments measure 

 about one-fourth of an inch wide and one-half inch long. There is no ali- 

 mentary tract, the office of absorption of food being filled by the skin. 

 Motion is effected by muscular bundles situated beneath the skin, which 

 give a variety of vermicular movements. A primitive nervous organi- 

 zation has been described. The entire length of the worm is traversed 

 by two canals connected in each joint l\v a cross system. This system 

 is said to serve as an excretory apparatus. It has been called a vascular 

 system. Each adult segment contains a complete hermaphroditic gen- 

 erative apparatus. The3^ begin to appear in the first third of the animal 

 and gradually mature toward the last segment. At about the middle 

 the eggs become fertilized and develop until the end. The terminal seg- 

 ments when ripe separate aiid pass away. In this way tlie segments, 

 which were once near the head, become central and finally' terminal, 

 growing adult, maturing their embryo, and passing away in turn. The 

 embryonic shells are 0.036'"'", about one-seven-hundredths of an inch 

 thick. The embryo is six-hooked. These worms mature and liberate 

 segments in the dog in about ten or twelve weeks after the eysticercus 

 has been swallowed. 



Occurrence. — The marginate tape-worm is found at about the mid<lle 

 of the small intestine, therein differing from Twnia serrafa, T. ccemirus, 

 and T. cuciwierina, which live nearer the end of the small intestine. 

 They may be found in dogs of any age. Shepherd or collies, hounds, 

 and slaughterhouse dogs are most liable to be infected. City dogs; 

 which have but little opportunity of being infected, rarely contain the 

 parasite. 



Disease. — The harm that the parasite does the dog seems to be in- 

 considerable. Were it not that the ci/sficcrcal stage does harm to sheep, 

 it might well pass unnoticed by the fiock master. The ease with which 

 one can rid his dogs of the parasite seems to [)lace the destruction of 

 the species in his hands. For Tccnia marginata alone the administra- 

 tion of an effective trenicide every two months would be sufficient; 

 but as T. cwmirus develojis in three or four weeks, it would be best to 

 treat for both at once and dose the dogs more frequently. 



Diagnosis. — Every sheep-owner should proceed to dose his dogs with 

 worm medicine, whether they are known to have t;ipe-worms or not. 

 The diagnosis of tape-worms in dogs is difficult, those having many 

 often showing no symptoms. Sometimes they may be suspected from 



