When first extracted, the Trichina is usually disposed in two or two and a half spiral coils : when straightened out (which is to be done with a pair of hooked needles, when the sur rounding moisture is so far evaporated as that the adhesion of the middle of the worm to the glass it rests upon shall afford a due resistance to a pressure of the needle upon the extremi ties), it measures 4,th of an inch in length and of an iuch in diameter, and now requires for its satisfactory examination a magnifying power of at least 200 linear admeasurement.
The worm (fiz. 55) is cylindrical and fili form, terminating obtusely at both extremities, which are of unequal sizes ; taper ing towards one end for about one-fourth part of its length, but continuing of uniform diameter from that point to the opposite ex tremity.
Until lately it was only at the larger extremity that I have been able to distin guish an indication of an orifice, and this is situated in many specimens in the centre of a transverse, bilahiate, linear mouth, (a, fig. 54.) A recently extracted living worm, when ex amined by a good achromatic instrument be fore any evaporation of the surrounding fluid has affected the integument, presents a smooth transparent exterior skin, inclosing apparently a fine granular parenchyma. It is curious to watch the variety of deceptive appearances of a more complex organization which result from the wrinkling of the delicate integument. I have sometimes perceived what seemed to be a sacculated or spiral intestine ; and, as eva poration proceeds, this has apparently been surrounded by minute tortuous tubes; but the fallacy of the latter appearance is easily de tected. A structure, which I have found in more recent and better preserved specimens than those which were the subjects of my first description, is evidently real, and may pro bably belong to the generative system of the Trichina ; it consists of a small rounded cluster of granules of a darker or more opaque nature than the rest of the body ; it is situated about one-fifth of the length of the animal from the larger or anterior extremity, and extends about half-way across the body.
Dr. Arthur Farre, whose powers of patient and minute observation and practised skill with the microscope, are well known to those who have the pleasure of his acquaintance, discovered, by theexamination of recent Trichina under favourable circumstances, that they pos sess an intestinal canal with distinct parietes.
Ile describes it as commencing at the large end of the worm, bounded by two parallel but slightly irregular lines for about one-fifth of the length of the body, and then assuming a sacculated structure which " becomes gradually lost towards the smaller end where the canal assumes a zig-zag or perhaps spiral course, and at length terminates at the small end." In a recent examination of some Trichina from an aged male subject at St.Bartholomew's llospital, I perceived a transverse slit close to the small extremity on the concave side, which I regard as the anus.
The muscles which are affected by the Tri china are those of the voluntary class; and the superficial ones are found to contain them in greater numbers than those which are deep seated; the pectoralis major, latissimus dorsi, and other large flat muscles usually present them in great abundance. They have been detected in the muscles of the eye, and even in those belonging to the ossicles of the ear, and of whose actions we are wholly uncon scious: they also occur in the diaphragm, in the muscles of the tongue, in those of the soft palate, in the constrictors of the pharynx, in the levator ani, in the external sphincter and, and in the muscles of the urethra. But they have not yet been detected in the muscular tunic of the stomach and intestines, in the detrusor urines, or in the heart. It is an inte resting fact that all the muscles infested by the Trichina are characterized by the striated ap pearance of time 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 retieularly united.
From the instances of this parasitical affec tion of the human body which have already been recorded, and from other unpublished cases in which I have examined the worms, it is evident that their presence in the system is unconnected with age, sex, or any particular form of disease. They have been found in the bodies of persons who have died of cancer of the penis; tubercles in the lungs ; exhaustion of the vital powers by extensive external ul ceration of the leg ; fever combined with tu bercles in the lungs; aneurism of the aorta; sudden depression of the vital powers after a comminuted fracture of the humerus ; diar rhma.