ANIMAL PARASITES AND DISEASES. 53 



Dr. Fantham also experimented with ferrous sulphate, ten grains 

 introduced into a gallon of drinking water. In this connection I 

 would point out that I have obtained very encouraging results from a 

 much stronger solution ojL ferrous sulphate ; indeed, anything that 

 will help to raise the general tone of vitality of the birds, will probably 

 aid in resisting the action of the parasite, and for this purpose ferrous 

 sulphate seems admirably adapted. 



MEDULLARY GID IN LAMBS. 



The occurrence of medullary gid in lambs is by no means common 

 in this country. Ordinary gid or staggers is fairly common, indeed 

 in some years particularly prevalent. This I have described in some 

 detail in my Fifth Report, 1 from which I quote the following life- 

 history. 



A dog infected with Taenia caenurus the. species of tapeworm, 

 scatters the eggs and gravid segments on the ground. In moist 

 places these may live for some weeks, but if exposed to hot, dry 

 weather, they soon die. 



Both sheep and cattle swallow some of these eggs when either 

 drinking or grazing. Once they reach the stomach of the host, the 

 digestive juices dissolve the shells of the eggs and set free the embryo. 



These embryos then commence and bore their way out of the 

 intestine into the tissues. Some make their way into the blood 

 vessels and are carried into the different parts of the body. Only 

 those, however, continue to develop which reach the brain or spinal 

 cord. The embryo now commences to burrow along the surface of 

 the brain, and in a few days becomes stationary, forming a tiny visicle 

 or bladderworm. At first this is about one-eighth of an inch in 

 diameter, but on the twenty-fourth day it is the size of a pea. By the 

 thirty-eighth day it is the size of a cherry and the heads begin to 

 grow, new heads appear, but none reach their full development until 

 the end of two or three months. 



When such a brain is eaten by a dog the wall of the visicle is 

 digested, but the heads remain uninjured and attach themselves to 

 the wall of the intestine and develop into adult tapeworms. In about 

 eight or nine weeks the posterior segments of the worm become filled 



1 5th Rept. Inj. Insects, 1908, p. 50. 



