TRICHINA SPIRA'LIS, the name given to a peeoli.ir nematoid worm, which, in its sexually immature state, inhabits the muscles usually of the pig. It was discovered in 1835, Mr. Wormald, then demonstrator of anatomy at St. Bartholomew's, giving to prof. Owen four microscopical specimens of speckled muscle from a subject that was then in the dissecting-rooms; and Mr. Paget, then a first year's student, simultaneously investi gated the question. Prof. Owen, to whom the discovery of the trichina is generally referred, soon afterward communicated to the zoological society his "Description of a Microscopic Entozoon infesting the Muscles of the Homan Body," in which he describes the 7peckles as capsules containing a spirally-coiled microscopic worm. to which he gave the generic name trichina (Gr. thrtz, a hair), and the specific name spiralis, from its coiled arrangement. Mr. Paget had independently arrived at similar results, with the aid of Robert Brown of the British museum, and read a paper on the subject to the Aber nethian society a week before prof. 0 wen'smemoir was read to the zoological society; so that his name should always be at least associated with that of Owen, in reference to the discovery of this worm. From the dale of this discovery to the present lime, the has been a fertile source of discussion. In 1b43 the idea was mooted by various naturalists that the trichina was the undeveloped or soxless form of sonie other worm; and in 1855 (after the transformatiim of the cysticerens into the tapeworm was discovered), various suggestions were made on this subject ; but it was not till 1860 that Virchow and Lc:tick:1n, by feeding animals on flesh containing trichina?, arrived inde pendently at the correct conclusion, that the parents of the encysted trichina: arc small nemitoid worms, which had never previously been described, Leuckart's experiments being made with human flesh containing these parasites.
The young trichinm, as they are seen in the human muscles, present the form of spirally-coiled worms, in the interior of small, globular, oval, or lemon-shapeal cysts, wl.ich appear as minute species scarcely visible to the naked eye. These cysts are more
or less covered externally with calcareous matter, according to the length of time they have remained in a fixed position, and the degree of degeneration which their walls have undergone. The trichina measures, according to Cobbold, on an average of an in. in length, and of an in. in breadth. The cysts are sometimes altogetner absent, and hence they must be regarded as abnormal formations, resulting from local in liamation sei, up by the pzesence of the worm, which in this larval condition of existence of an in. in length, and of an in. in breadth. These larval worms ex hibit a well-marked digestive apparatus, and afford evidence of the presence of repro ductive organs, which are often sufficiently developed to enable the observer to deter mine the sex of the organism. The number of larval trichina? that may shnulta»eously exist in the muscles or a single man or animal is enormous. In a cat on which Leuckart experimented, a single ounce of flesh was estimated to contain 1125.000 trichina?; and if all the voluntary muscles of a human body of ordinary size were similarly affected, the number of worms would exceed 1930 millions! Dr. Cobbold believes that there can he no doubt that the number in a single "bearer" (as he terms the sufferer) may amoitnt to at least 20,000,000.
We now proceed to the consideration of the mature worms. When an animal is fed with flesh containing the larval worm already described and is killed a. few days after ward, a large number of minute worms are found mixed with the contents of the small intestines. On closer examination, they arc found to be of two kinds—the. larger and more numerous ones being the females, and the smaller and rarer ones the males. At the second day after their introductien, these intestinal trichime attain their full sexual maturity; and in six days the females contain perfectly developed and free embryos its their interior.