The bothriocephalus latus, in its general appearance, resembles the two varieties of henia just described, but is rather larger and may grow to a greater length. The mature joints are broader than they are long, and the 0.
sexual openings are placed, not at the side of the segment as in the Mania, but in the middle of the joint, where they appear as rosette-shaped patches. This tape-worm, like others, has an intermediate or larval stage ; and it had long been suspected that its ciliated embryo found shelter in the body of some aquatic animal. Dr. Braun, of Dorpat, has lately found the early asexual form of the bothriocephalus encapsuled in the intestine of the pike, and also in some of the muscles, in the liver, and in the spleen of the same fish. Dr. Braun gave these organisms experimentally to dogs and cats, who were put on a strict diet and allowed only distilled water for drink. As a consequence, segments of the bothriocephalus began quickly to appear in the faeces of the animals.
Causation.—The means by which thread-worms gain access to the human body, is by the direct passage of the ova into the mouth. The eggs are often introduced clinging to fruit, tresses, and various articles of food. But they may also be directly conveyed to the mouth by the patient him self. It has been said that the embryo is liberated from the egg in the child's stomach by the action of the gastric juice upon the ovum. It has been also stated that each individual female worm contains in itself a multitude of eggs which pass out in large. quantities with the stools. The embryos are probably not liberated from the ova in the bowels ; but if the ova are re-introduced into the alimentary canal by the mouth, they become exposed to the action of the gastric juice in the stomach, and their contents may be set free. According to Dr. Cobbold, children frequently carry the ova under their nails ; for the irritation to which the presence of the oxy ures gives rise, obliges them to seek relief by scratching. In this way the eggs may be transferred directly to the mouth.
The ova of the lumbricus appear to be imported through the medium of impure water. This parasite is said to be especially common in low lying, marshy districts.
In the case of the tape-worm, it is through the eating of imperfectly cooked flesh infested with the cysticercus that an individual becomes the unwilling harbourer of the parasite. The toenia solium is derived from measly pork ; the tEenia medio-canellata from beet In children who suf fer from a chronic looseness of the bowels, and are consequently fed with pounded raw meat, tape-worm is occasionally met with.
most varied symptoms have been ascribed to the presence of worms in the bowels. Most of these are doubtless due to the intestinal derangement from which the patient is commonly suffering. That they are not a necessary consequence of the lisits of these parasites is shown by the fact that it is not rare for the creatures to be found in the stools of children who have not previously exhibited any sign of discom fort or distress. In these cases, the worms are usually few in number, and can be readily got rid of by the administration of an ordinary aperient. It seems necessary for the extensive propagation of the entozoa that a ca tarrhal condition of the bowel should be present. In the secreted mucus the embryos find a favourable medium for development, and if, as often happens, the flux be profuse, great difficulty may be experienced in free ing the patient from these irritating pests. It is in such cases only that severe general symptoms are found ; but these, as has been said, are to be rightly attributed, not to the parasites, which may be looked upon as acci dental complications, but to the unhealthy state of the alimentary mucous membrane, which hinders digestion and impairs the nutrition of the body. These symptoms are described elsewhere (see page 121), and need not be here repeated. There are, however, many special symptoms which are at tributed directly to the presence of worms ; and as they are not necessarily the consequence of the intestinal derangement referred to, and often cease when a number of worms have been expelled, it is possible that they are really due to the irritation set up by the creatures in the bowels.