780 PARASITIC DISEASES. 



rot-affected slieep have been pasturing, to destroy the diseased 

 animals themselves, and, after a time, to restock with sound 

 animals. 



There can be little doubt that this method would prove 

 effective for a while ; but since, to insure a permanent result, 

 a frightful sacrifice would have to be made in the first instance, 

 it is to be feared that the experiment could not be undertaken 

 without severe and rather unconstitutional legal enactments. 

 Moreover, supposing the colony were rendered entirely free from 

 rot, the original exciting cause, which we are told brought the 

 malady into the country somewhere about the year 1855, might 

 again reintroduce the disorder. On this subject, however, the 

 reader will do well to consult the notice of Dr. Eowe's observa- 

 tions, as recorded in the Veterinarian for February 1873. In 

 perusing the communication in question, it should be borne 

 in mind that the observations proceed from the pen of an 

 observant and extensive stock-owner. 



CESTODA. 



This natural order of flat-worms has acquired its name from 

 the circumstance that most species in the adult condition 

 resemble a tape or band, hence also the common name tape- 

 worm. Sometimes, however, the resemblance to a tape fails 

 altogether, as is conspicuously the case with the little tape-worm 

 of the dog {Taenia ecliinococcus). The absence of a mouth and of 

 an alimentary canal are very characteristic of the order, so that 

 in the tape-worm we have an animal feeding by the process of 

 osmosis. 



If an adult tape-worm be examined we find that it consists of 

 segments. The anterior segment is differently constructed from 

 all the rest, and is variously designated as the head, nurse, or 

 scolcx. Behind the anterior segment or head follows a chain of 

 segments for reproductive purposes, the generative segments or 

 2yroglottides. These generative segments are produced by a 

 process of budding from the head. In the same worm we find 

 them at all stages of development, unripe, half-ripe, or com- 

 pletely ripe segments, the youngest nearest the head. It is 

 quite important to observe that the head produces all the rest of 

 the worm by a process of budding, so that if all the body be 



