GID OR STAGGERS. 



T^NIA CCENUEUS, KucL. 

 Plate XI, Figs. 1 to 4. 



The disease whicli is popularly known as gid, sturdy, staggers, or 

 turusick in sheep, is caused by the presence of a i)arasite living in the 

 brain. This parasite is closely related to Twnla marginata. It lives in 

 about the same way, but differs from it in detail. It is known as T. 

 cwnurus in its adult state, and as Gmnurus cerebralis in its cystic state— 

 the stage in which it infests sheep. 



Method of infection. — Sheep become infected with this dangerous para- 

 site while pasturing or drinking where dogs have scattered the eggs in 

 their wanderings Ihrough the country. In the West tLe eggs may also 

 be scattered by the wolves, coyotes, and foxes, which may harbor the 

 adult parasite. 



lAfe history. — The eggs of Twnia cwnurus, after being taken with the 

 food or drink, are hatched within the stomach of the sheep and make 

 their way through its walls. They then migrate either actively, by 

 forcing their way through the connective tissues, or passively, as is 

 generally believed to be the case, by getting into the circulatory system, 

 and are carried from thence into various portions of the body. Those 

 arriving in the spinal canal and cranial cavity seem to thrive and grow, 

 while the others, which may have reached the heart, lungs, and dia- 

 phragm, grow for a time and then perish. 



Description of cystic ste^ce.— Having arrived in the brain cavity, the 

 •young embryo migrates upon the surface of the brain much as the em- 

 bryo of Taenia marginata does through the liver substance. The gal- 

 leries it makes are sinuous. They begin at a point and slowly increase 

 with the growth of the parasite and run in any direction. In from two 

 to three months after the first invasion of the brain the cysts have 

 grown as large as a hazel-nut, or about a half inch in diameter. When 

 examined closely they will be found incased in a thick outer skin, a sac 

 made by the membranes ot the brain. . Out of these sacs the parasites 

 may be loosened, and these resemble the cysts of T. marginata. It 

 differs, however, in a very important particular — instead of having a 

 single knob attached, tens or hundreds of these knobs may be seen as 

 little dots hanging from the inner surface into the fluid of the cavity, 

 (see Figs. 3 and 4). Each of these dots can evert itself, or push its head 

 out^ ?i»d will tbeu be seen by the aid of a glass to be a perfectly de- 



83 



