is the cause of the bladder-worm, producing sheep-gid, or sturdy (_Cœnurus cerebralis_). This tapeworm, which may live in the intestine of other animals besides the dog, has a circlet of hooks, is from fourteen to sixteen inches long, and consists of about two hundred joints. It generally lives in the intestine of the sheep-dog, in correspondence with which is the fact that the bladder-worm lives in the brain of young sheep. If a sheep-dog harbours _Tænia cœnurus_ in its stomach, a sheep may very easily take up a joint with grass or heath. The joint is then digested in the sheep’s intestine, and the larva escapes from the egg. It bores through the wall of the sheep’s intestine, gets into the circulation, and is carried by the blood-stream to various parts of the body; it can only develop further, however, in the brain (or spinal cord). After the minute larvæ have reached the cavity of the cranium they move about on the outer surface of the brain, and dig out channels there till they find a suitable place for further growth. The larva now becomes a bladder-worm, which gradually grows, until it attains a size varying from that of a nut to that of a hen’s egg. It develops numerous tapeworm heads, even from three to four hundred. These become tapeworms if a sheep is killed by the parasite, and its head devoured by a dog or fox. The disease caused by the presence of bladder-worms in the brain is called “gid,” or “sturdy,” also “staggers.” Two stages can be distinguished in it. During the first period the symptoms of disease are chiefly due to the wounds which the larvæ make on the surface of the brain, and the consequent inflammation of the investing membranes. Even in this stage the disease may be fatal, but the symptoms cease as soon as the larvæ cease to move about. The bladder-worms are only able to do harm by the pressure they exert, which is small at first, though it gradually becomes greater. The first stage of gid manifests itself in late summer, the second in late autumn, winter, or spring, according to the rate at which the bladder-worms develop. The symptoms of the first stage are caused by the increased flow of blood to the brain and head generally, resulting from the irritation which the larvæ exert. (Head very hot. Eyes bloodshot. The sheep are sluggish but restless, and carry their heads in a strange way, to one side, bent back, or turned up. They often run round in a large circle. There may also be gnashing of the teeth, foaming at the mouth, squinting, convulsive movements, and loss of consciousness.) The symptoms of the disease in its second stage are the result of pressure on the brain and some of the arteries of the brain and skull. (The sheep affected separate themselves from the others, and generally hang their heads. Gaze fixed. Occasional loss of consciousness. Movements strange; run or turn round in a circle. The sheep often staggers and falls to the ground. The bones of the skull