containing the acephalocysts and echinococcus, are composed of condensed cellu. lar tissue, and are of a laminated texture. Occasionally they become hardened by the deposition of earthy matter, feeling gritty upon pressure. On tearing open the cyst, which may be done with a cataract needle, in the field of the microscope the worm is discovered within, disposed in two or two and a half coils, and surrounded by a transparent fluid. The trichina measures from 1-25th to 1-30th of an inch in length, and 1.700dth of an inch in diame. ter. It is cylindrical and filiform, termi

an intestinal canal, with distinct parietes; and Mr. Owen has more recently perceived a transverse slit close to the small extremity, which he regards as the anus.

The trichina appears to be chiefly, if not entirely, confined to the muscles of volition; and those which are superficial, such as the pectoralis major and platysma myoides, usually contain them in greater abundance than the muscles which are deeply seated. In addition to the larger voluntary muscles, they have been detected in the muscles of the external ear and of the soft palate; also in the constrictors of the pharynx and in the levator and sphincter ani. They have not yet, however, been found in the heart, in the muscular tunic of the alimentary canal, or in the muscular fibres of the bladder. It is an interesting fact, noticed by Mr. Owen, that all the muscles infested by the trichina are characterized by the striated appearance of the ultimate fasciculi; while the muscles of organic life, in which they are absent, have, with the exception of the heart, smooth fibres, not grouped into fasciculi, but reticularly united.

The presence of these worms in the system does not appear to be connected with age, sex, or any peculiar form of disease. They have been found in the bodies of persons who have died of tubercles in the lungs, aneurism of the aorta, and hectic fever. No painful or inconvenient symptoms were present, in these cases, to that, in all instances, the patient himself excite any suspicion of a morbid state of the muscular system, and it is probable is unconscious of the presence of the microscopic parasites which are enjoying their vitality at his expense. Although they are so minute in size as scarcely to be perceptible to the naked eye, yet, when present, they exist in such countless numbers, and their distribution throughout the muscular system is so extensive, that it was imagined they must occasion debility, from the quantity of nutriment required for their support. This opinion, however, is not sustained, for I have found the trichina in the muscles of two robust men, who were killed while in the apparent enjoyment of good health; one by fracture of the skull, the other by fracture of nearly all the ribs, with laceration of the lungs the first was 58 years of age, the other 60.

The occurrence of the trichina is certainly rare, but they were found during the last winter, once or twice, in most of the dissecting rooms in London. I have myself observed them three times, whilst conducting post-mortem examinations, and I have met with them once in dissection. It is, however, a curious fact, that my brother, Henry Curling, who was constantly engaged during last season, in

Clamart's large dissecting rooms, at Paris, where the number of bodies admitted exceeds those dissected at all the schools in London, did not hear of any instance in which this worm was discovered; though having been but recently described, it would not have been liable, if present, to have escaped detection. The only specimen seen by Giraldi, one of the most diligent of the prosectors there, had been brought over from England. The distinguished physiologist, Müller, who visited this country in the autumn, informed me that he had met with it in Germany.

The Sterelmintha, or third class of the Human Entozoa, contains five genera. We shall speak first of the

5. Cysticercus Cellulosa,

(from KUOTIS, a bladder, and Kepkos, a tail). It consists of a head, neck, and dilated cyst, of a spheroidal form. Of the genus Cysticercus there are several species, distinguished for the most part by the forms and proportions of the neck, or body, intervening between the head and the cyst. The only species known to infest the human body is the Cysticercus Cellulose, which

Cysticercus Cellulosa.

is developed like the trichina, in the cellular tissue between the fibres of the muscles, and is also included in a similar adventitious cyst. The head of this parasite is furnished with a beak, or proboscis, armed with a double circle of hooks, for irritation and adhesion, and four promi

Magnified head of Cysticercus Cellulosa. nent suckers, for imbibing the surrounding nutriment, the fluid secreted by the adventitious cyst in which they are lodged. The head and neck are usually retracted within the cystic pouch, their situation

being indicated by a white opaque spot in the transparent vesicle.

The occurrence of this entozoon in the human subject appears to be rare, especially in this country. It is less uncommon on the continent. Rudolphi relates, that out of two hundred and fifty bodies dissected annually at the Anatomical School of Berlin, from four to five were found, through nine consecutive years, to be infested more or less abundantly with the Cysticercus Cellulosa. Bremser, however, endeavoured for ten years to procure them at the Great Hospital, and in the Anatomical Amphitheatre of Vienna, but in vain. The development of these animals is not limited, like the Trichina, to the voluntary muscles, for they have been discovered in the heart and oesophagus, and also in parts not muscular, as the brain, especially the plexus choroides, and in the eye. The muscular tissue around the cyst is not otherwise diseased.

Portion of Human Muscle with Cysticercus
Cellulosa.

Soemmering first observed this parasite in the anterior chamber of the eye, in the case of a young woman aged 18. In the course of seven months it became twice as large as when first observed, and attained the size of a pea. On being extracted through a small incision in the cornea and put into warm water, it continued to move for more than half an hour. It then became gradually opaque and white; and with the microscope the four suckers and the double circle of hooks, forming the head of the animal, were plainly discerned. The Cysticercus Cellulose has been detected since, in the anterior chamber of the eye of a lively healthy child, seven years of age, after an attack of ophthalmia, by Mr. Logan, of Scotland, in 1833. It floated unattached in the anterior chamber, was about two lines in diameter, and of a spherical form, except that a slender process was seen to be projected or elongated from time to time, and again retracted, so as to be completely hid within the cystic portion. It interfered with vision, more or less, according to its position, and the form which it assumed. As it subsequently enlarged in size, so as to impede the motions of the iris, and excite inflammation in the sclerotica and conjunctiva, it was extracted through the cornea, at the Glasgow Eye Infirmary. The animal was torn in shreds in the operation, but the

result was satisfactory as regards vision. Cysticerci sometimes occur in the brain in considerable numbers. Treutler once found fifteen in one plexus choroides, and two in the other. They are not, however, so common as the simple serous cysts, for which they may be mistaken. In the brain of an epileptic patient, who died in the Bicêtre at Paris, Cruveilhier found at least a hundred of these animals. Some were seated in the sub-arachnoid cellular tissue of the brain and cerebellum; others occupied the substance of the convolutions, and central part of the hemispheres. As many as fifty were observed in the structure of the cerebellum, and others were discovered around the spinal cord.

I know of no symptoms by which the presence of these parasites in the muscles can be recognised, nor any mode of treatment by which they can be expelled the system.

The Cysticercus Cellulose likewise occurs in quadrupeds, and is found most commonly, and in greatest abundance, in the hog, occasioning that state of the muscles which is vulgarly termed "measly pork." In two measly pigs dissected by Andral, cysticerci were found in the subcutaneous

and intermuscular cellular tissue, in the different folds of the peritoneum, and in the liver, lungs, and substance of the heart.

The Canurus, or polycephalous hydatid, which is so frequently developed in the brain of the sheep, and is the cause of the affection known under the denomination of the "staggers," does not occur in man.

6. Tania solium,

or common tape-worm of this country. The Tania solium consists of a flat, elongated, articulated body, varying in breadth from one-fourth of a line at its anterior part, to three or four lines at its widest, from whence it again diminishes to its termination. The head, which is so small that it cannot well be seen without the aid of a strong lens, is somewhat hemispherical, and provided on its anterior surface with a prominence, encircled by a double row of minute recurved processes or hooks, which are surrounded by four suckers or mouths. The circle of minute hooks are not constantly found, and Bremser supposes that they disappear with age. The anterior joints of the neck are very short; those immediately follow

ing are nearly square, their length scarcely exceeding their breadth; the remaining ones are long, the last series of the segments being sometimes twice or three times as long as they are broad. The first articulation is received into the base of the head, and each subsequent joint is let into the one in front of it. Both longitudinal and transverse fibres may be observed in the larger specimens of the Tania. Each segment possesses distinct and separate motions, the fibres not being continued from one joint to the other. A tænia, when recently expelled, is occasionally contracted to the length of a few inches, the segments appearing as closeset transverse striæ; but after remaining for a few hours in water, it may be found to measure as many feet. Werner states, that a tænia which extended from the anus of a patient to the length of three feet, returned itself almost entirely into the intestine. Other and still more extraordinary instances of the powers of motion possessed by tæniæ have been noticed; and it is without doubt to this cause that we must attribute the circumstance, that a part of the body of one of these worms is sometimes found to be tied in a complicated knot, a specimen of which is preserved in the museum. From the four

Tania tied in a knot.

mouths already described proceed two vessels, which run along the whole length of the animal, near the margins of the joints. These, which are the nutrient vessels, arc united by transverse canals at each joint; and they terminate, according to Rudophi, in a common orifice in the last joint. In a large specimen of tapeworm, in which the nutrient vessels were injected with quicksilver, they were found to pursue a regular serpentine course; and as in repeated trials the mercury could only be made to pass in one direction, viz. towards the posterior extremity, I

Portion of a Tania magnified, shewing the Nutrient Canals and Generative Organs. conclude that they are furnished with valves. All the articulations have marginal foramina which open alternately, that is to say, on the opposite edges of two contiguous joints. Thus, of the two free margins of each articulation, commonly one only possesses a pore; this, however,, is by no means invariable, and in some instances there are two pores on each joint. In each joint there is a large branched ovarium, from which a duct is continued to the marginal opening. The ova are crowded in the ovary; and in those situated in the posterior segment of the

body, they generally present a brownish colour, which renders the arborescent form of the ovary sufficiently conspicuous. A duct more slender and opaque than the oviduct, and containing a grumous secretion, may be traced extending from the termination of the oviduct at the lateral opening, to the middle of the segment, where it terminates in a small oval vesicle. This is the male duct and gland, and the ova are impregnated in their passage outwards. The structure, therefore, of the generative apparatus in the Tania is androgynous, each segment of the individual being sufficient for reproduction,

It has been a question whether the nutriment of the tape-worm is imbibed through the pores which I have described at the sides or margins of each joint, or whether the entire body is dependent for its nourishment upon the four mouths from which the lateral canals commence. Rudolphi and Mr. Owen are of opinion that the lateral or marginal orifices of the segments are exclusively the outlets of the genera tive organs In some species of tape. worm, in which no ovaria have been detected, there has been a corresponding absence of the marginal pores, while the lateral longitudinal canals have been present and of the ordinary size. In other species the generative pores open upon the middle of one of the surfaces of each segment, and in these it is plain that the lateral nutrient vessels have no communication with the central pores. The orifices of the segments correspond, in short, with the modifications of the generative apparatus, while the nutrient canals undergo no corresponding change. We may conclude, therefore, that the head of the tania is the sole natural instrument by which it imbibes its nutriment, and it is to the expulsion of this part that our attention should be chiefly directed in endeavouring to relieve a patient from these injurious parasites.

The tania solium measures usually from five to ten feet. It has often been found much longer. Tape-worms twenty feet long are by no means rare. Robin relates in one of the French journals that he once found one extending from the pylorus to within seven inches of the anus, which would make its length at least thirty feet. Cases, however, are recorded in which they have attained the length of a hundred feet, and even more. Some of the accounts, such as a case mentioned in the Copenhagen Transactions of a worm measuring eight hundred ells, are not perhaps altogether worthy of credit. The name of tenia solium, or solitary worm, is not strictly applicable to it, as it is well known that it may co-exist with several others of its own or even different species.

Bremser has frequently known two or three worms to be passed simultaneously by the same individual. As the joints are very readily separated, you must be careful not to mistake several portions of one worm for different parasites. It is, indeed, rather rare to find a tænia of any size entire, the larger tape-worms being found almost always torn across, and deprived of the final articulations. Sir A. Carlisle conceived that the detached joints were capable of becoming distinct animals, but later investigations have shewn this opinion to be erroneous.

The tania solium is met with in the principal countries of Europe, but not in all with equal frequency. It is common in England, Holland, and Germany; and travellers relate that it infests the inhabitants of Egypt.

Tapeworms generally reside in the small intestines, where it does not appear that they produce any important lesions. It is not often that we have an opportunity of ascertaining the state of the intestinal canal when they are present. I examined the body of a female twenty-three years of age, who had passed portions of tapeworms by stool for several years, and who had voided part of a very large one by the mouth the day before death, but although a large tænia was found in the ileum, the only lesion in the intestinal canal, which was examined carefully throughout, was a very slight hypertrophy of the follicles, chiefly of the glandulæ solitaria. There was no preternatural injection of the vessels. They have been found adhering pretty closely to the mucous membrane by means of the circle of hooks, and it has been imagined that they might occasion ulceration and even perforation of the intestine; but I do not know of any wellauthenticated case in which they had produced so unfortunate a result.

The statements of various writers respecting the effects of tape-worms upon the economy differ considerably, some representing them as exciting scarcely any disturbance, whilst others regard them as the source of very serious mischief. Rudolphi speaks of them as existing in very healthy individuals, and only being detected in consequence of portions being found in the stools. Such may sometimes be the case, but there can be no question that in general they occasion more or less derangement in the system and impairment of the general health. The best account of the symptoms occasioned by these animals is by Louis, and it is drawn up with all the care and accuracy which characterize the productions of that distinguished pathologist. It results from his observations, that the origin of tænia cannot be ascribed to bad nourishment, a weak state