Another and more formidable entozoon, communicable by unsound meat, is the Echinococcus hominis,[31] which represents one of the metamorphoses of the Tinea echinococcus, the tapeworm of the dog. In Iceland, where a sixth of the population are said to suffer from the ravages of the Echinococcus hominis, it is the custom to feed the dogs on the flesh of slaughtered animals affected with this parasite, which in the body of the dog develops into a tapeworm. The innumerable eggs which the worm produces are, however, incapable of being hatched in the dog’s intestines. They have to find another and more suitable habitat, and this is secured for them as follows:—Segments of the tapeworm, with their countless ova, being voided with dog’s excrement, fall into the running water, and on to the fields and pastures, whence they gain their entrance into the stomachs of human beings, oxen, and sheep. Here the eggs become hatched, not into tapeworms, but into Echinococci hominis, or prospective tapeworms. Burrowing through the
membranes of the stomach, the echinococcus establishes itself most commonly in the liver, but not unfrequently in the spleen, heart, lungs, and even the bones of man. In the animal economy they enclose themselves in little sacs or cysts, and give rise to the most alarming and painful diseases, which hitherto have proved incurable. They attack the brain in sheep, and are the cause of the disease known as “staggers.” Sheep are also infested by another parasite known as the Distoma hepatica, the ravages of which give rise in the sheep to that devastating disease—“the rot.” The creature is also known by the name of the “liver-fluke,” since it principally attacks this important organ in the animal. The liver-fluke is of constant occurrence in the livers of diseased sheep, and unless destroyed by thorough cooking will of course pass into the human economy. The embryo fluke gains admission to the sheep’s body through the instrumentality of small snails, to the shells of which it attaches itself. In wet weather the snails crawl over the grass of the meadow which forms the pastures of the sheep, and are swallowed by it. Once in the sheep’s stomach the embryo becomes a fluke, and commences its depredations on the animal’s liver. After this, the reason why the rot attacks sheep after a continuance of wet weather will be evident.
[31] See article “Echinococcus hominis.”
The most terrible of all the meat parasites is a minute worm about 1⁄30th of an inch long, found in the flesh of pork. This creature, which is named the Trichina spiralis (from the form it assumes when coiled up in the little cyst or capsule which encloses it), when it gets conveyed into the human stomach with improperly cooked or underdone pork, soon becomes liberated from its confinement owing to the destruction of its envelope by the gastric juice. Once in the stomach the parasite grows rapidly, giving birth to innumerable young trichinæ, which, by first boring through the membranes of the alimentary canal, pierce their way through the different parts of the body into the muscular tissue, where they become encysted, and where they remain until conditions favorable to their liberation again occur.
Until such time, however, as they have become enclosed in the cyst, their movements give rise to indescribable torture, and to a disease known as trichinosis, of which it has been estimated more than 50 per cent. of those attacked by it die. The symptoms of trichinosis commence with loss of appetite, vomiting, and diarrhœa, succeeded after a few days by great fever—resembling, according to Dr Aitken, that of typhoid or typhus. As might be expected the pains in the limbs are extreme. Boils and dropsical swellings are not unusual concomitants of the malady.
Hitherto this frightful disease has been mostly confined to Germany, where there have been several outbreaks of it since its discovery
in 1860 by Dr Zencker. Feidler says that only free trichinæ are killed by a temperature of 155° F.; and that when they are in their cysts a greater heat may be necessary. From what has been said the importance of efficient cooking must become manifest. There must always be risk in underdone pork, whether boiled or roasted. In the pig, the trichina, if present, may always be found in the muscles of the eye. In Germany the makers of pork sausages are now said to have these muscles subjected to a microscopic examination previous to using the meat, which, of course, is rejected if the examination has been unfavorable.
The trichinæ, if present in the flesh of pork, may be seen as small round specks by the naked eye, the surrounding flesh itself being rather darker than usual owing to the inflammation set up in it. All doubt, however, on this point may be removed by having recourse to the microscope. Dr Parkes says a power of 50 to 100 diameters is sufficient, and that “the best plan is to take a thin slice of flesh, put it into liquor potassæ (1 part to 8 of water), and let it stand for a few minutes till the muscle becomes clear; it must not be left too long, otherwise the trichinæ will be destroyed. The white specks come out clearly and the worm will be seen coiled up. If the capsule is too dense to allow the worm to be seen, a drop or two of weak hydrochloric acid should be added. If the meat be very fat a little ether or benzine may be put on it in the first place.”
Legislation relative to meat inspection and seizure.—The law recognising the importance of the supply of pure and wholesome meat gives considerable powers to the different sanitary officers who are appointed to inspect it. See Food, Inspection of.
MEAT, AUSTRALIAN. See Meat preserving.