The tapeworm that ranks next in importance to the tania solium is the tcenia medio eanellata, which was first established as a distinct species by Blichenmeister only a few years ago. It exceeds the T. solium both as regards length, breadth, and the thickness of the individual segments; the head is also somewhat larger, abruptly truncated at the crown, destitute of a proboscis and a hook-apparatus—hence this species has been described as the hookless furnished with very large sucking-disks, sur rounded by much dark pigment, which gives the head a blackish appearance. The specific name of mediocanellata has reference to an interesting and almost specific char acter in connection with the water-vascular system, into which we have not space to enter. Leuckart has proved by experiment that the measles or cysticerci which pro duced this worm are to be found in the muscles and internal organs of cattle. He administered proglottides of T. mediocanellata to three calves, a sheep, and a pig. In the two last-named animals they produced no effect, as was shown by their post-mortem examination; while in the calves they produced a kind of leprosy, which has since been characterized as "acute cestoid tuberculosis," and which proved fatal if too large a dose of eggs was administered. On examining one of these animals after its restoration to health-48 days after the eggs were swallowed—he found numerous cysticercus-vesicles, larger and more opalescent than those of the pig, lodged in the muscles; and as the heads of the contained cysticerci exhibited the distinctive peculiarities presented by the head of the adult worm, "we are supplied with the most unequivocal evidence that man becomes infested with this second form of tapeworm by eating imperfectly cooked veal and beef." Hitherto the two above-described species have commonly been included under T. solium, from want of due examination, especially of the head. Dr. Cobbold believes that their respective frequency will ultimately be found pretty well on a par, though probably the T solium will maintain a slight ascendency, in consequence of the relative cheapness of pork. "Admitting occasional exceptions," he observes, "the hooked worm infests the poor, and the hookless worm the This circumstance accords with the fact, that the lower classes subsist chiefly upon pork, while the wealth ier prefer mutton, veal, and roast beef."—Entozoa, p. 243. It gives rise to the same symptoms as the T solium.
The next five tapeworms infesting man may be passed over without notice, as being of very rare occurrence. Tank acanthotrias is only known from a single case, in which, in the larval stage, it was found in the muscles of a woman. The last species we shall describe, the T. echinococcus, is, in its larval condition, probably more fatally injurious to the human race than all the other species of entozoa put together. In its mature (strobila) condition, in which it is found only in the dog and wolf, it seldom exceeds the fourth of an inch in length, and develops only four segments, including that of the head. The final segment, when sexually mature, equals in length the three anterior ones, and contains as many as 5,000 eggs. The proscolex or embryo forms large proliferous vesicles, in which the scolices or larvae (knctwn also as acephalocysts, echinococci, echinococcus beads or vesicles, pillbox hydatids, etc.) are developed by gemmation internally. The eggs develop in their interior a six-hooked embryo, and these embryos are introduced into our bodies with food or water into which the eggs have been carried. " With an especial liking for the liver," says Dr. Cobbold, " they bore their way into this organ, or are carried along the circulating current to other organs. In these situations they sooner or later become transformed into simple vesicular, bladder-like bodies, commonly called acephalocysts or hydatids." Instead, however, of displaying the head, neck, and body of a cysticercus, the vesicle retains a globular figure. Its growth is slow, and many months elapse before echinococci are developed within our bodies, after we have swal lowed the proper tapeworm eggs and their contained embryos. There have been great differences of opinion among physiologists as to the mode of development of these echi nococci; but the following is probably the current view: The inner surface of the vesicle presents after a time slight papillae or prominences, which, as they enlarge and become oval, are eventually scoleci form, and contain a cavity filled with a limpid fluid. This
scolex-like development produces in its interior a brood of scolices or echinococcus heads, or, in other words, becomes gradually transformed into the so-called " brood capsules" of helminthologists. It is almost impossible to explain the nature of these brood-capsules, with young echinococci in their interior, without the aid of such dia grams and illustrations as are given by Cobbold in his chapter on T. echinococcus. In the fully developed state the echinococci vary from to in of an inch in diame ter. The rostellum supports a double curve.of hooks, those in the smaller row varying in size from to of an inch, while those of the larger series are from s to of an inch. Below the hooks are four suckers, and the general appearance of the body is finely granulated, from its containing calcareous particles. It often happens that the discovery under the microscope of a few of these little hooks at once decides the nature of an otherwise mysterious tumor. Of 373 cases of the parasite occurring in man, collected by Davaine (who devotes more than one-third of his Trait des Entozoaires to this subject, 165 affected the liver, 40 the lungs, 30 the kidneys, 20 the brain, and 17 the bones, while the remainder were spread over other parts; and of 136 cases collected by Cobbold, 51 affected the liver. No less than 35 of these 51 cases recovered. "Four of them were complete natural cases; two others being also temporarily cured in the same. All the rest were cured by surgical operations." It is impossible to state with accuracy the degree of prevalence of hydatids in this country, or the extent to which it proves fatal. In Iceland this disease is endemic to such a degree that about one-sixth of the population are affected with it. It produces a long illness, terminating with a painful death, and no means of cure have yet been discovered. Its prevalence in that island may be rationally accounted for. Firstly, every peasant has, on an average, six dogs, all of which are probably infested by the mature tapeworm; 'and secondly, there being only six legally authorized medical men, the great majority of the population (over 10,000 persons, scattered over 1500 sq.m.) are in the hands of quacks, whose principal treatment consists in the administration of fresh dog-excrement! Our authority for this astounding specimen of homeopathic treat ment is Leuckart, whose admirable popular essay, On the Newest Discoveries regarding Human Intestinal Worms, and their Importance in Relation to hygiene, in the Conversations Jahrbuch (1863), is deserving of the most careful study. For an excellent abstract of the remarkable series of experiments—extending from 1851 to the present day—by which the relationship between the so-called cystic worms and the cestoid worms was estab lished, we may refer the reader to Aitken's Science and Practice of Nedicine, vol. i.; while for the subject of tapeworm generally, the highest authorities are the works of Kalien ineister and Siebold, translated by the Sydenham society; Davaine's 1Wcite des Ento zoaires; Weinland's Essay on the Tapeworms of Man; Lueckart's Das Menschlichen Para siten (not yet completed); and Cobbold's Entozoa (1864), a work equally remarkable for the vast amount of original research which it contains, and for the beauty and correct ness of the illustrations.
Tapeworms, although rare among horses and cattle, are common in dogs and sheep, causing irritability of the bowels, and an unthrifty appearance. For dogs no remedy answers as well as powdered areca nut, of which 30 grains suffice for a dog weighing about 20 lbs. It is best given after 10 or 12 hours' fasting, in a little soup or milk, and should be followed in a few hours by a dose of castor oil. Neither areca nor any of the approved remedies used in men, prove effectual in sheep; and one of the best prescrip tions for them consists of 40 drops of oil of turpentine, a dram of powdered green vitriol, and an ounce of common salt, given mixed in a little milk or gruel, or, where their bowels are confined, in linseed oil. A daily allowance of linseed cake and sound dry food should likewise be given with the grass or roots, and pieces of rock-salt left within the animal's reach.