DISEASES OF SHEEP 563 



sheep which circles may be suspected of having gid even though the 

 presence of the (Estrus larvae is also indicated. 



THE ERADICATION OF GID. 



Knowing the life history of the gid parasite, the eradication of 

 the disease becomes a very simple matter. It is only necessary to 

 step in at some point where the parasite is most easily attacked and 

 prevent its further development. This is accomplished in two ways : 

 first, by destroying the heads, or at least the brains, of sheep dying 

 of gid ; and second, by keeping sheep dogs or other ranch dogs free 

 of tapeworms. Of these two steps the first is much the more impor- 

 tant, for the reason that it is much more practical and effective than 

 the second and also is much easier. 



NECESSITY FOR DESTROYING HEADS AND BRAINS. 



Claims have been made to the effect that the destruction of the 

 heads of giddy sheep is unnecessary, on the ground that dogs do not 

 eat sheep heads. In a former publication* the writer has shown the 

 unlikelihood of scientists being mistaken as regards the life history 

 of the gid parasite, and has shown by experiments that a dog not 

 only would eat a sheep head, but having once eaten one, would sub- 

 sequently go for the brains first of all when given a sheep head. It 

 was shown that a dog would at times eat a skull so completely as to 

 leave almost nothing, and at times lick the brains out through the 

 foramen magnum and leave the skull apparently intact; in neither 

 case would there be anything to suggest to the casual observer that a 

 dog had eaten the brains. 



The shepherd dog used in the experiment described in the arti- 

 cle referred to, was fed an unskinned sheep head after an interval 

 of over nine months since the first experiment. The first day some 

 of the outer parts only were eaten in seven hours. After an interval 

 of a day the head was fed again, and this time it was picked down to 

 the bones, but the brain case was not entered. The remainder of the 

 head was left overnight and the next morning examination showed 

 that the dog, following the method used on the former occasion, had 

 licked out the brain through the foramen magnum, the opening 

 where the spinal cord enters the brain. This opening had been en- 

 larged little, if any, by the dog's teeth. A sheep head fed about a 

 week later was treated the same way. The meat was eaten off the 

 skull the first day and the brain licked out the evening of the second 

 day. 



It may safely be asserted that an adult coyote would have as 

 little difficulty in getting at the brains as a dog would. A sheep 

 brain covered with a lime-and-sulphur dip and one covered with a 

 coal-tar dip were fed to the coyotes. Small parts of the brain covered 

 with the lime and sulphur were eaten at once, in seven hours half of 

 it was eaten, and in twenty-four hours it had all been eaten. The 

 brain covered with coal-tar dip had been only partly eaten in the 

 same time. After being fed one regular meal the coyotes were given 

 one sheep brain covered with 40 per cent formaldehyde and one cov- 

 ered with turpentine. Eighteen hours later the coyotes had eaten 

 *Bureau of Animal Industry Circular 159. 



