more pointed, and the two lie so near each other that half a turn would bring them together. The bodies in the cavity of the sac are partly solidified by a calcareous deposit of gritty and almost crystalline texture, brittle, breaking on firm pressure, and composed, probably, of phosphate of lime, slowly deposited, so as to give to the extremities of the sac an opaque appearance and a firm consistence.

In this condition it was presented to the observation of medical men for some twenty-five years after its discovery. They were cases of old encysted trichina. They did not exhibit any distinct sexual apparatus, nor appear to produce any distinct symptoms by their presence in the human organism.

Between 1850 and 1860, certain experimenters in Germany, administered portions of muscle, infected with this parasite, to the lower animals; and they found-especially Luckhart who was the most successful in these investigations-that these worms, so small and incomplete in development, so long as retained in the muscular system, became further developed after introduction to the intestine of another animal. After a short time the sexual apparatus appears, copulation takes place, the female produces living young, which penetrate finally into the muscular system of the second animal and there domicile for an indefinite time. These experiments showed the muscular system of the pig, cat, rat, mouse, rabbit and one or two other species of the inferior animals could be infected with trichina. So far nothing more had been learned with regard to trichinosis as a disease in the human subject. In 1860 an epidemic of trichinosis occurred in Germany. The members of a family in Dresden were taken sick with symptoms similar to those of acute rheumatism mingled with those of typhoid fever. One of them, a servant girl, died, and her muscles were found filled with trichinæ. The attending physician and Professor Virchow gave the trichinous muscles to a rabbit, which became infected with the parasite, and died in four weeks time. The infected tissues of a rabbit were given to a second, which became likewise infected and died in about four weeks. A third rabbit fed on the flesh of the second with a similar result. Hence the disease as

it exists in man, may be transmitted to the lower animals, and from one to another indefinitely, the parasites passing alternately from the intestines to the muscular system, and from thence to the intestines.

In old cases of this disease their anatomical structure is not made out easily; but in recent ones from the recent use of trichinous flesh, its anatomy can be made out with more distinctness. About five years ago, some sailors on board ship in this port were taken sick with symptoms like those in the Dresden family. It was found that the disease, in their cases, originated from eating raw pork or bacon. About the same time the disease became developed in some permanent residents of the city; and was traced to the use of imperfectly cooked ham; a portion of which I examined, and found that the parasites were in a decidedly different condition from that in cases of long standing. The cysts containing the worm, instead of having definite and rounded ends, gradually tapered off into long and slender prolongations, the ends of which were intricately entangled with the muscular fibre. In these drawings you see represented the cysts containing the trichinæ, as found in the ham (Fig. 2.) In this case the cyst is evidently a hollow, fusiform tube, consisting of a transparent and structureless, but well developed membrane, containing the worm coiled up. From the two ends of this fusiform cyst run off the prolongations, the structure of which is evidently tubular, and their cavity is nearly continuous with that of the sac containing the worm. Not quite so, however, for a membranous partition runs across where the prolongations begin, so that the worm is enclosed in a distinct cavity; and the prolongations are tubes of much smaller calibre, but were apparently at some previous time connected with the central cavity. This cavity contains a transparent fluid, by which the worm is separated from the membranous walls. Breaking open the sac by a slight pressure between the glass plates, it ruptures and discharges the worm, which escapes in such a manner as to show that it lay before perfectly free within the cavity of the sac. (Fig. 3.) You will usually find much difficulty in uncoiling the worm sufficiently to examine its struc

ture. No operation in microscopic anatomy requires more patience than this; for its firm folds must be unwound without rupturing any of its parts, in such a manner as to give you a fair view from one end to the other. (Fig. 4.) At this stage it is found to be one twenty-eighth of an inch long; its head tapering and pointed, and the body very gradually enlarges from the anterior extremity towards the middle, near which is its greatest diameter which it retains throughout the rest of its extent, terminating posteriorly in a round, blunted extremity. The alimentary canal runs the whole length of the worm, a mouth at the pointed end, and an anus at the rounded end. About the junction of the middle with the posterior third of the parasite, the calibre of the canal suddenly contracts, then enlarges again; afterwards it remains reduced to about one-third its original size. The only other organ visible at this time is that which together with the alimentary canal, occupies the posterior third of the worm; an organ apparently tubular, rounded at the ends, and full of rather large and tolerably well-defined cellular bodies. This evidently is the sexual apparatus as it exists at this time.

Suppose now a portion of muscle filled with trichinæ in this condition be taken as food by man or by one of the lower animals. On arriving in the small intestine, the worms are found to be perfectly free, for the muscle, as well as the cysts in which they were contained, are digested in the stomach, so that within twenty-four or forty-eight hours you find an abundance of free trichinæ in the cavity of the duodenum. At once they begin to increase in size, so that, usually by the fourth or fifth day they have become three or four times as large as before. They have arrived at the adult condition; the sexual apparatus has become perfect, and copulation of the sexes takes place. I have, on several occasions, found in the intestine of the rabbit, the two sexes in copulation, the male fastened upon the female at the orifice of the generative apparatus. The eggs having been impregnated, as the animal is viviparous, the female soon becomes full of the young brood,

In the drawing you see these parts as just described. (Fig. 5.)

Instead of the intestine taking up the whole of the anterior twothirds of the body, and a great part of the posterior third; the sexual apparatus is by far the most prominent organ in the interior of the body of the female; and as soon as the young have arrived at the period of development here represented, they begin to move forward to the terminal duct of the generative apparatus. This can now be seen very clearly, running from the Ovary forward to a point quite near the anterior end of the worm. The young are very numerous, and in this way are discharged into the cavity of the small intestine, begin the boring process through its mucous membrane, and undoubtedly pass through the entire thickness of the intestinal walls, causing much irritation, which is the first symptom of trichinosis. It is usually sufficient to produce a considerable degree of pain, and not unfrequently a smart attack of diarrhoea. After passing the walls of the intestine, they disperse in every direction, and from that time you begin to find them in the muscular tissue throughout the body. Within a fortnight after the symptoms have began to manifest themselves in the human subject, you will find them almost everywhere, scattered throughout the voluntary muscles. They increase but little in size during their transit, so that when they first arrive in the muscular tissue they are only 1-140th or 1-120th of an inch long. They soon became encysted and increased in size. At first they are not enclosed in distinct sacs, but are contained in the interior of long tubes.

The sac in which the encysted trichinæ is contained, is often connected with prolongations running out from each end, and in the human muscle within the first fortnight of infection, the young worms are found contained in swollen tubes. This is the condition of the worm as it was found in the muscles of the human subject on the 13th day of illness, in a case which I examined. The worm, you see, is not free, but is contained in the interior of a tube, swollen or fusiform at the point where the worm lies partly coiled up. The worm is not stationary at this time, but by gentle pressure can be made to move from one end to the other of the swollen portion of the tube. By about the end of the first fortnight its coils assume a considerable degree

of regularity, and the worm then reaches that condition which has given it its name of trichina spiralis.

How did it get in the muscular tissue, and what is the nature of the tube it inhabits, and which is to become its cyst? Most German observers believe this tube to be a muscular fibre; that the worm passes from the intestine to the remotest regions of the body by boring its way through the intermuscular cellular substance; and that if examined on its first arrival there, it is perfectly free; that it then penetrates the substance of the muscular fibre, producing atrophy and degeneration of its substance, until the fibre becomes converted into the tube, with prolongations as described. On the other hand, it is possible that the worm may also be transported by the circulation; for if it can bore through the walls of the intestine, it can also penetrate the blood-vessels, and it might thus finally reach the left side of the heart, and be sent with the current of circulation to every part of the body. However it is certain the young trichina arrive at the muscular tissue by working through the intervening cellular tissue, or are distributed by the blood-vessels. They very soon present themselves in the interior of the swollen tubes, which may be capillary vessels that have become plugged, by coagulation of the blood, or by deposit of the exuded material excited by the presence of the worm; or muscular fibres that have undergone degeneration and atrophy from its presence. Soon the tube containing the parasite suffers a further alteration. An exudation takes place around the worm, so that the part of the tube containing it is shut off from the rest; and the rest of the tube becomes atrophied into slender, tapering prolongations. After some years these also entirely disappear, and leave only an ovoid sac without prolongations; and finally you may have the cavity of the cyst invaded by a calcareous deposit-the last peculiarity of the degenerated cyst.

All these changes in its history have been seen in the human subject; the development of the young in the body of the female; the discharge into the intestine; penetration into its walls, and dispersion to the muscular tissue throughout the body; their domiciliation in the interior of the tubular cavities, and