DISEASED PORK, AND MICROSCOPIC WORMS

IN MAN.

BY JOHN GAMGEE,

PRINCIPAL OF THE NEW VETERINARY COLLEGE, EDINBURGH.

Did Moses know more about pigs than we do? Was it a knowledge of the parasitic diseases common to man and swine which led the father of the Jews to condemn pork as human food? Both questions can be answered in the negative; and the apparently slender grounds on which pigs were first regarded as unclean are stated in the following verse: "And the swine, because it divideth the hoof, yet cheweth not the cud, it is unclean unto you: ye shall not eat of their flesh, nor touch their dead carcase." The wisdom of the Mosaic law can only be justly estimated with a knowledge of the accidents arising in warm countries from eating pork throughout long and hot periods of the year; and there is no doubt that the direct evil results as manifested by human sickness led to the exclusion of pork from the list of Israelitish viands. The masses of measly pork which may be seen hanging from the butchers' stalls in Southern Europe prove that the long-legged swine which hunt the forests for acorns, and rove about to pick up all kinds of offal, are often unfit for human food; and that they were so to no less extent in the land of Israel is probable. There are those who fancy that domesticity breeds disease that improving the meat-producing powers and hastening the growth of our live stock renders it liable to disorders of a malignant type -no greater fallacy! The parasitic maladies which are bred for man in the systems of the animals we eat are most common in the quadrupeds allowed to rove about in search of food, and which living amongst men and animals, have every opportunity of meeting with the germs of the worms which prey on them. The animalcules which burrow and breed in the human frame are not, as the ancients believed, the results of an agglomeration of unhealthy humours becoming vitalized when perfected in form. The advocates of the spontaneous generation theory are now few and far between, and the development of the lower forms of animal life in apparently inaccessible regions of the human frame, only affords an illustration of how wonderfully every precaution is taken in the

ordinary routine of Nature's works to prevent the extermination of the smallest and apparently most useless of living creatures. The wisdom of creative design is not easily fathomed when we see the higher orders of animals, and man himself, perishing in order to afford food and a means of propagation to the marvels of organization which appear to us always obnoxious and destructive-born for evil, and not calculated to play in this world's role any other than an offensive part.

It is interesting to observe that parasitic maladies in the pig specially abound in that section of the United Kingdom where swine live most amongst human beings. The Yorkshire and Berkshire pigs, in their native counties, enclosed in the farm-yards of their breeders, are free from worms which are likely to live in the body of man. The Irish pig is the one most commonly injured by entozoa, and the reason for this is evident when we know how much the cottager relies on rearing a porker which is permi.ted the free range of house and road, where every description of filth is devoured, charged with the ova of parasites expelled by man, or some of the lower animals. The observations of helminthologists prove that it is not unattended with danger for human beings to sleep together when one is affected with tapeworm or trichina. How much more dangerous, then, for animals to live with people who disregard all habits of cleanliness! Though we may ridicule the notion that filth breeds parasites, we must not forget that dirt protects the ova, and secures their transmission from one nest to another. The terrible hydatid disease, which is the direct cause of one-fifth of the human mortality in Iceland, is due to negligence and dirt. The Icelanders slaughter their animals, and leave the offal to decompose. Dogs naturally devour the entrals, which abound in entozoa, and, breeding tapeworms within them, disseminate eggs over the whole country, so as to ensure the development of bladder-worms in the internal organs of the herbivorous quadrupeds, which the people eat. The conditions under which we live in the British Isles are certainly much less favorable to the propagation of worms; but we disregard, in our ignorance, the most common precautions to protect ourselves from loathsome diseases, and not only permit dogs to eat any kind of offal in and around slaughter-houses, but sanction the existence of piggeries where all kinds of garbage, charged with worms or their eggs, are daily devoured by swine. The majority of germs calculated to engender parasites are to be found in abundance in the contents of the alimentary canal of human beings and domestic quadrupeds. If pigs are permitted to eat these, as in Ireland or in many British piggeries, we must expect hams, bacon, and pork sausages, to be charged with the embryonic forms of human entozoa. Whereas, in Iceland, then, the dog

is the victim of human negligence, and en revanche the cause of human disease, in the British Isles the pig holds this unenviable position; the more however we learn of parasitic disease in man, the better we can understand how even the underdone roast beef of Old England may prove to us poison as well as food, and how the dog or cat we pet may indirectly shorten our days. We have good reason to believe with Moses that the pig is an unclean beast; but without discarding him from the scanty list of animals to be eaten, it is evident that we can purify the race of swine, and thus prevent human as well as porcine maladies.

Having thus drawn attention to the general causes operating in the production of parasitic affections, a brief reference to the most important of those common to human beings and the pig may not be devoid of interest. I wish to refer more especially to the one least understood, and which is occasionally attended with fatal results-viz., trichinous disease in man and animals.

Though Mr. Hilton, demonstrator of anatomy at Guy's Hospital, and Mr. Wormald, at St. Bartholomew's, had repeatedly noticed a peculiarly speckled condition of the voluntary muscles of the human frame prior to 1835, it was only in the month of February of the latter year that Professor Owen first described the smallest of human parasites, which we now know to be common, and to exist, as Owen first said, in "astonishing numbers." The case which afforded Professor Owen the opportunity of securing for this country the honor of one of the most brilliant discoveries in helminthology, was observel by another of our distinguished countrymen, Mr. Paget. It is not a little remarkable that we should owe to the Germans the history of the parasite before it reaches the human system; though this is a direct result of the intelligence and earnestness with which Küchenmeister and his followers have carried out so-called "feeding experiments," whereby they have determined the origin of human parasites, and the identity of entozoa seen in different animals under such a variety of forms, as to have led to each form being considered a distinct species, whereas it was only a stage of a singular metamorphosis. In 1852 Herbert fed three dogs with the trichinatous flesh of a badger, and found the parasites in the muscles of these dogs. Some of the first feeding experi ments to trace the origin of trichina in man, were performed in Edinburgh, by the members of the Physiological Society, whose labors were of too short a duration. Specimens of the parasite were shown to the Society on the 19th of March, 1853, by Dr. W. T. Gairdner, who, with his usual acuteness, declared that the whole appearance of the parasite was such as seemed strongly to bear out Owen's view, that the trichina was merely the first stage of an animal destined for further development. Dr. Gairdner

thought it very probable that the muscle was only the hot-bed of ova, which, for their development into perfect animals, required some other habitat. Considering it to be not unlikely that this further development of trichina might take place in the intestinal canal of some carnivorous animal, Dr. Gairdner sent some of the specimens exhibited, in the fresh state, to Mr. Barlow, who administered portions to dogs and cats; and I learn from Dr. Mercer Adam that the result of the experiments was as anticipated by Dr. Gairdner. The results were not published, and we owe to continental observers and to Mr. Turner, of the Edinburgh University, interesting information as to the propagation of the parasite.

Professor Owen's first description is in many points complete. In his paper communicated to the Zoological Society of London he says: "With a magnifying power of an inch focus the white specks in the muscles are seen to be cysts of an elliptical figure, with the extremities in general attenuated, elongated, or more opaque than the body (or intermediate part) of the cyst, which is, in general, sufficiently transparent to show that it contains a minute coiled-up worm. On separating the muscular fasciculi, the cysts are found to adhere to the surrounding cellular substance by the whole of their external surface, somewhat laxly at the middle dilated part, but more strongly by means of their elongated extremities, so as to render it generally a matter of some difficulty to detach them. When placed upon the micrometer they measure 1-50th inch in their longitudinal and 1-100th inch in their tranverse diameter; a few being somewhat larger, and others diminishing in size to about one-half the above dimensions, They are generally placed in single rows, parallel to the muscular fibres, at distances varying from half a line to a line apart from one another; but sometimes a larger and a smaller cyst are seen attached together by one of their extremities, and they are occasionally observed slightly overlapping each other. If a thin portion of muscle be dried and placed in Canada balsam, between a plate of glass and a plate of talc, the cysts become more transparent, and allow of the contained coiling-up worm being more plainly

seen.

"Under a lens of the focus of half an inch, the worm appears to be inclosed within a circumscribed space of a less elongated and more regular elliptical form than the external cyst, as if within a smaller cyst contained in the larger, like the yolk of an egg surrounded by its albumen and shell. The worm does not occupy more than a third part of the inner space. A few of these cysts have been seen to contain two distinct worms; and Dr. A. Farre, who has paid much attention to the subject, has shown me

a drawing which he made of one of the cysts containing three distinct worms, all of nearly equal size.

"The cysts vary in form as well as size, being more or less elongated, and the opaque extremities being further extended in some than in others in a few instances only one of the extremities is thus produced. Occasionally the tip of one of the extremities is observed to be dilated and trans parent, as though a portion of the larger cyst were about to be separated by a process of gemmation."

The coiled parasite is seen in the centre figure of the annexed plate,* and the peculiarities of the worm are well brought out from the imbibition of an ammoniacal solution of carmine-a method of preparation which often enables us to trace the characters of microscopic objects which are otherwise ill defined. The body of the parasite is seen clothed with a transparent skin, which does not imbibe the carmine so readily as the softer structures within. The thickness of the skin has been estimated by Leuckart at 0.001dth millimetres. Attention has been drawn by Henle, Luschka, Küchenmeister, and others, to the wrinkled appearance of this skin, which in all perfect specimens is smooth, and not convoluted Leuckart says that when the parasite is injured, rings round the body are commonly visible. The skin is structureless. Beneath the skin is a layer of fine granular matter with the appearance of longitudinal stripes and numerous bright refrangent corpuscles. This has been looked upon as the muscular structure of the trichina.

From the cutaneous muscular structure there are two bands, or water tubes, stretched from before backwards on the lateral part of the body. The centre pale, but with well defined outlines, and striated alongside of them are small round or oblong yellow corpuscles.

The alimentary canal extends through the whole body from the narrow end or head to the broad anal extremity. The organs of generation do not appear in the encysted worms, and only when they attain their full development in the alimentary canal of their host, though the females are distinguish able from the males even in the capsule.

Without entering into further details as to the worm, it is important to notice the capsule that surrounds it, and which consists of the thickened sarcolemma, and a special envelope for the capsule within this. Leuckart has demonstrated that the trichinæ lead to the removal of the muscular tissue, and are really living in the muscular fibre itself. They are therefore not, as some persons have supposed, in the areolar tissue between the muscular fibres; and the fact of their existence in great numbers occupying the place of the active muscular element, explains symptoms in marked cases of trichinous disease.

The plate is omitted.-KLIPTART.