This species has been found in adults, but is more common in children from three to twelve years of age. The number of this species existing in a human body is variable. Sometimes only two or three are found. At other times a hundred, and even twice that number, are voided in a few days.
(2.) The ascaris vermicularis, thread, pin, or seat-worm, is round, very slender, and about half an inch in length. The habitation of this species is the rectum, and they are often found matted together in the excrement. They are very active, even after ejection, and have been known to cause great local irritation by entering the vagina and urethra. Their presence is an occasional cause of masturbation. It is impossible to estimate the number of these parasites that may exist in the human rectum. Great numbers, sometimes, are voided at a single evacuation.
(3.) The tricocephalus dispar is a third variety of the round worm, and is said to infest the bodies of almost every species of mammalia. As its name indicates, the upper portion of its body is slender, hair-like, and terminates at the lower extremity in a thick, spiral portion. It is from one to two inches in length, and is found attached by its head to the mucous membrane of the cæcum, and, in rare instances, in the colon and small intestine. They are rarely numerous.
Tæceniæ or tape-worms, are hermaphrodites, of a flat, ribbon-like form, and are composed of numerous segments, each of which is provided with a complete set of generative organs, and contains ova for the production of thousands of individuals. Some authors have supposed that each segment, or joint, is a distinct individual, but the existence of one head for the whole precludes this theory. There are two species of tæniæ developed in the human intestine; the tænia solium and the tænia lata.
(4.) The tænia solium is the species commonly found in America and all the countries of Europe, except France, Russia, and Switzerland. In France, both species are found, but the tænia lata seems to be indigenous to Russia and Switzerland.
The tænia solium varies in length from four or five to thirty, thirty-five, or even forty feet. The head is hemispherical and armed with a double row of twenty or thirty hooklets. The genital organs are alternate and placed upon the outer edges of each segment. It inhabits the small intestine, and is usually solitary.
(5.) The tænia lata, or broad tape-worm, is distinguished by the greater breadth of its segments, and the location of the genital organs, which are found in the centre of each segment. Its small elongated head is unarmed, and has a longitudinal fissure on each side. It usually attains a greater length than the tænia solium.
Symptoms. The symptoms which the long worms occasion, are frequently somewhat obscure. Thirst, irregular appetite, colicky pains, excessive flow of saliva, enlargement of the abdomen, itching of the nose, pallor of the face, offensive breath, disturbed sleep, and grinding of the teeth, all are common symptoms. Occasionally, convulsions and other nervous affections are produced by the presence of the ascaris lumbricoides, but generally they produce less constitutional disturbance than the other varieties. The passage of this species of worms from the bowels, or their ejection from the stomach, is the only positive evidence of their presence. The ascaris vermicularis, thread, pin, or seat-worm, gives rise to most of the symptoms produced by the long worms, but in addition produces intense itching at the anus, and, not unfrequently, an eruption upon that part. The itching is particularly distressing at night. When the little sufferer is well covered, the warmth occasioned by the bed-clothes causes these little parasites to crawl out upon the anus, and produces such paroxysms of itching and pain as to cause the child to kick the covering oft and lie naked. The persistent manifestations of a disposition to lie naked, should excite the parents' suspicions of seat-worms, and lead them to investigate all the symptoms. By examining the child's stools the worms may he found adhering to the feces, and they may also be seen on the anus. Thousands of children suffer untold agony from these little seat-worms, which are left unmolested to torment them, because the parents are unfamiliar with the meaning of the symptoms manifested, and therefore pay no heed to them. We have been thus particular in describing the symptoms indicating the presence of these pestiferous parasites, in order that they may be readily detected.
The Symptoms produced by the tape-worm are dizziness, ringing in the ears, increased secretion of saliva, indigestion, ravenous appetite, sharp abdominal pains, and emaciation. The only positive sign of the presence of these parasites, is the passage of pieces of them in the feces. The nervous and other symptoms produced by the ordinary long worms are also caused by the tape-worm.
Causes. Careful observations have proved that there are certain causes which favor the generation or development of intestinal worms. Among others, we may mention fatty or farinaceous articles of food, gormandizing, constant exposure to a moist atmosphere, and sedentary habits.