The Cestode or tape-worms include the Taenia or ordinary tape-worms, and the Cysticerci or bladder-shaped worms, Hyda tids.
The phenomena of disease induced by the Cestode, or tape worms, are all related to foods, and the relationship is singularly exhibitive of the success of scientific experimental research in its application to medical and sanitary science.
The tape-worm is the cestode with which the community is most familiar; but it is, in fact, one only of several phases of a distinct parasitic growth. It does not enter the body as tape worm, but is derived from a larval form which is present, usually in the encysted state, in the fleshy or visceral parts of animals that are consumed as food.
The commonest tape-worm in the human subject is the Tenia solium, a flat, ribbon-like worm, divided into numerous segments, and reaching sometimes a length of many feet. The longest I have seen extended to sixty feet, but some observers have spoken of a length far exceeding even that. This worm is derived from the hydatid known technically as the Cysticercus cellulose. The embryo of the Cysticercus, swallowed accidentally by an animal which is to become human food, the pig for example, enters the alimentary canal, pierces the mucous surface, migrates along the cellular or,connective tissue, and becomes embedded in the inter muscular spaces. In this position the embryo undergoes develop ment into Cysticercus cellulosic, and so, infesting the flesh of the animal, gives rise to that diseased condition of food commonly known as measly pork.
The measly food is the source of the tape-worm. By hooklets with which it is armed, the living Cysticercus connects itself with the wall of the bowel of him who swallows it, and sprouting, as it were, from the attachment it has made, becomes the many segmented, long, flat tape-worm.
There is another side to the question Of induced diseases from the cestodes. The imperfect cestode worms from which the tape worms are developed, are, in their turn, the causes of diseases which were characterized by the old writers as hydatid diseases, and which amongst the people are still known by that general name. The hydatid disease originates from the tape-worm, and a simple illustration of the fact is derived from the history of parasitic disease in the inferior animals. The dog is commonly infested with the tape-worm called the Tenia coenurus. The sheep is infested with an encysted hydatid, the coenurus which affects its brain, and gives rise to the disease called the " staggers" or " sturdy." If a sheep be fed with tenia from a dog the coenurus will be produced in the brain of the sheep; and if a dog be fed with coenurus from a sheep the tape-worm will occur in the intestine of the dog. Experimental researches have since proved that the two forma of disease can be thus, reciprocally, induced.
The illustration extends to the human subject. A little tape worm which is found in the dog, and is called the Tenia echino coccus, yields a larval form which is cystic, the bladder-worm, or hydatid of man, Echinococcus Hominis. In its embryonic state this parasite, introduced into the intestinal canal by food or water, permeates the tissues, and becomes in time encysted in one or other of the vital organs. The liver is the organ most frequently attacked, but no organ is actually free from invasion. The em bryo in due course becomes developed into an easily recognizable animal form enclosed in its cyst. It has a head with a double crown of booklets, a body containing calcareous particles, and four suckers.
Through what precise articles of food or drink embryo of the echinococcus is introduced is not yet completely known; but the experimental evidence of introduction by alimentary substances is demonstrative.
Symptoms of Cestode Disease.
The phenomena of disease caused by the cestodes are many and important. The tape-worm is a source of constant irritation, and the knowledge of its existence in the body often causes much depression.
The most dangerous forms of disease from parasites are those which follow the insertion and development of the true hydatid, the echinococcus, in the tissues and vital organs. The as if it had a roving commission, plants itself in the most various and important viscera. The brain, the spinal cord, the eyeball, the lungs, the liver, the intestinal glands, the kidney, the urinary bladder, the muscles, and even the cavernous portions of bone itself, are homes in which it may live.
In consultation with the late Dr. Herbert Barker of Bedford, I once saw a man who threw off the echinococcus by the renal secretion, and we traced in this instance the mode of entrance of the larvae of the tenia.
The man had for years subsisted almost altogether on fresh pork, in so far as animal food was concerned, and twice weekly had feasted on pig's fry, a dish made up of the intestinal part of the swine. On some one of these many feasts he had, by acci dent, partaken of a fry containing an embryonic parasite which the swine had picked up while feeding, and which had come from the tape-worm of a dog.
Trematode or Fluke-worm Disease.
Disease from the Trematode or fluke-worms is rare in man. In sheep, the liver fluke, Fasciola hepatica, is, as is too well known, a cause of most serious and extensive disease, and the same parasite has, in a few instances, not ten probably alto gether, been found in the human body. By some happy acci dent or necessity man has, up to this time of his history, missed the food that conveys this fatal enemy; an accident the more to be wondered at when it is known, as Cobbold truly says, that the liver of a single sheep may, at any given time, harbor several hundred specimens of the fluke, and that every mature specimen may contain many thousand minute eggs.
The fluke known as the Distoma Haematobia, or Bilharzia Haematobia — from the name of Dr. Bilhartz, its discoverer in sometimes a cause of fatal disease in Egypt, Mauritius, and the Cape of Good Hope. The adult male worm is nearly half an inch long, and is broad; the female is longer but nar rower than the male. The worm was first found in the portal veins of the infested subject, and the blood seems to be the seat in which it is located. Its ova make their way into the exeretogo organs, as the kidney, and may be voided by the urine. They give rise to great congestion of the affected organs, to irritation, and in worst cases to extravasation of blood. The mucous mem brane of the colon has been found charged with vegetative-looking growths filled with eggs of this parasite. The parasite or its ova probably finds its way into the body by means of drinking water.