TÆNIA, in zoology; a genus of insects, belonging to the order of vermes zoophyta. The body is of an oblong form; and composed of evident joints or articulations, in the manner of the links of a chain, with a mouth and viscera in each joint. See Plate cclxxxii.
1. The lata, long-tape-worm, or solitary worm, infests the intestines of man and some other classes of animals, and seems to derive its nourishment from the chyle that is prepared in the stomach.—This worm is long and flat, composed of many very short rings that are articulated to each other, and has a kind of vein running through its whole length, which is more or less apparent.—This has occasioned the Germans to give it the name of flat spines worm. It is not always of the same complexion; sometimes it appears of a blueish or reddish, and sometimes simply of a white colour; now and then it manifests itself only by a spot, which is to be perceived in the middle of each ring. In some of these worms this spot is of a blackish colour, in others of a colour more tending to white; and it rises into a very small prominence on each side, that is not easily apparent, however, to the naked eye. The tail or posterior end has never been capable of examination hitherto, because the worm breaks, and the patients void portions of it occasionally, either naturally or by the means of various remedies. Its body, which is usually several cells in length, and flattened like a rib-band, becomes gradually narrow towards its upper extremity, and at length terminates in a small thread-like appearance, of a foot or more in length. The point, which to the naked eye appears very minute, when examined by the lens, seems somewhat bulbous; and when viewed through a microscope that magnifies
powerfully, is found to be the head of the worm, and is terminated by four horns of unequal length, which are perhaps the channels through which the animal derives its nourishment. The body of the worm extends itself throughout the whole intestinal canal, and often reaches even to the anus. It has been named solitary worm, because there commonly exists only one in the same subject: sometimes, however, two of them are found together; and sometimes, after the expulsion of the first, there regenerates a second. It is by no means easy to remove this worm: the purgative vermifuge remedies commonly used in physic bring away portions of it, which we are always obliged to break, in order to separate them from those which remain behind; it seldom happens that they effect a complete cure.
2. The folium, or gourd-worm, resembles the former in many particulars, and is equally met with in the intestines of animals. It will be distinguished from the preceding one, by having neither the appearance of a head nor of a longitudinal vein: its rings are much longer than those of the solitary worm, and are striated through their whole length, being furnished only with a little lateral prominence. These rings are easily detached from each other, so that they appear as so many distinct worms, which have each of them life and motion independent as it were of the rest. The form of these rings, when viewed together, varies considerably. Those of the upper extremity are much more complete, short, narrow, and thin, than those lower down; the rings gradually becoming longer as they approach the lower end. These rings are in shape not unlike the seeds of gourd, and hence the name gourd-worm. Like the other, it is several cells in length, and is never voided whole, but by detached portions which fall of themselves.
For the methods of destroying and expelling those worms, see MEDICINE, no 493.