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find a bladder-worm in any other organ. Special search was made for them in the brain and spinal cord, but without success. As the bladder-worm, grows larger it frequently projects on the surface of the muscle, so that it may seem to lie external to it, and project, for instance, into the cavity of the abdomen. But even in such cases careful examination almost invariably shows a thin sheet of muscle-fibres spread over the projecting bladder-worm. When the eggs of the tape-worm are swallowed by the rabbit the secretion of the stomach destroys the strength of the shell, so that the embryo is able to escape. This embryo is armed with six hooks (see figs. 1 and 2, Plate I.), by means of which it works its way into the wall of the alimentary canal, and thus gains access either to the lymphatics or the blood-vessels. Thence it may be carried with the blood-stream to the various organs of the body. On reaching the ultimate ramifications of the blood-vessels the embryo appears to bore through the wall of some capillary. The commencement of the track found in early stages in the muscles may probably indicate the point at which it leaves the blood-vessel. We have seen that the bladder-worms are only found in the muscles, but we may readily believe that many embryos are led by chance to take up tkeir abode in other organs of the body, but that they fail to develop there. Even where the bladderworms were most numerous they only represented a very small proportion of the eggs which had been given to the rabbit. All rabbits are not equally susceptible to the bladder-worm disease. Some individuals seem to furnish a specially suitable home for the development of the bladder-worm, and great numbers of the parasites may be found in them. Sometimes the number is so great that they produce a considerable disturbance in the system, owing probably to the numerous points of local inflammation set up. Hence, such rabbits may die during the first two or three weeks after infection. Other rabbits, again, affording less suitable conditions for the development of bladder-worms, a comparatively small number of them are found. Yet other rabbits may enjoy complete immunity, the bladder-worm being quite unable to develop within them. Some of my.rabbits were fed several times with tape-worm eggs, but all attempts to infect them failed. I obtained evidence showing that the younger rabbits were more susceptible than the older ones; but on this point my observations were necessarily limited, as all the experiments were conducted on wild rabbits, and at the time of the year no very young rabbits were obtainable. But, although young rabbits are more susceptible, yet it is only some of the older rabbits which enjoy immunity from the disease. It is not easy to explain why some rabbits should afford so much better a home for the growth of the bladder-worm than others; but the phenomenon is not one confined to the particular bladder-worm of the rabbit which we are considering, but has been shown to occur in the case of other bladder-worms. I will only mention here the bladder-worm of the armed tape-worm of man (Tania solium). This bladder-worm is found in the pig. It is of small size, and forms the so-called " measles "of pork. Haubner fed five young pigs with abundant ova of Tania solium. Of these, two remained quite free from infection, a third contained only forty or fifty measles, another several thousands, and the last one still more. Leuckart fed five young pigs with very numerous ova: each of them received at least a whole tape-worm, whilst some of them were fed two or three times. On dissection, after the lapse of various intervals of time, the number of measles which were found to have developed were said to be respectively a single one, a few hundreds, two or three thousand, several thousand, and twelve thousand. Even in the last instance, where the measles were most numerous, only one per cent, of the eggs administered had developed. 3. Experiments on Carnivorous Animals with the Bladder-worm. As I have already mentioned, the chief carnivorous animals which feed upon the rabbit in the Wairarapa are the dog, cat, ferret, and hawk; and of these it is the first three which were open to suspicion as bearers of the adult tape-worm of which the bladder-worm is the larval stage. I endeavoured therefore to ascertain by experiment whether the bladder-worm, if given to these animals, would live in them and develop into the corresponding tape-worm. Two young ferrets and a young cat were obtained and fed several times with bladder-worms, which they swallowed greedily. But in all three animals the attempt to rear the tape-worm failed. Having already ascertained that the dogs in the district were often infested with tape-worm, it was still more desirable to try a similar experiment with dogs. It was undesirable, for obvious reasons, to do this with dogs from the district which might already contain tape-worms; and rabbits carrying bladder-worms were therefore taken up to Auckland, with the intention of experimenting there on dogs free from tape-worm. The diseased rabbits, however, died at sea, and it was found impossible to import more from the Wairarapa. I had fed rabbits with the ova of a tape-worm procured from a dog in the Wairarapa, and, after the lapse of a little over three months, bladder-worms had developed in these rabbits to a stage sufficiently advanced for experiments. Some of these bladder-worms were given to three dogs, the first two receiving each some three to four hundred heads, and the third two complete bladder-worms, each containing nearly three hundred heads. Of these three dogs, two developed the same kind of tape-worm, which agreed in its characters with the tape-worm found in the dogs in the Wairarapa, from the eggs of which the bladder-worm had been reared. To render the matter still more conclusive, proglottides of the tape-worm thus reared in the dogs were given to rabbits, and in the majority of these the Ccenurus was developed. 4. Characters of the Tape-worm (Taenia serialis) reared in the Dog. The tape-worm thus reared in the dog's intestine from the Ccenurus of the rabbit has a long, narrow, flattened form (see Plate 11., fig. 1). Its length may be from 16in. to 24in., though it may appear either longer or shorter, for the tissues of the body are contractile in a very high degree. It consists of a minute head, a somewhat narrower unjointed neck, and a series of joints or segments, which gradually increase both in length and witdh as their distance from the head-end

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