The embryo is frequently met with in sewage water, from which, if it be removed and placed in pure or distilled water, it soon dies. The embryo which does not become a distoma gives rise to a progeny (gradually formed from germ-cells within it) consisting sometimes of one, but much more often of a number of bodies of various forms and structures, each of which possesses powers of movement and locomotion. But the creatures of this second development are not distomata; neither are the offspring to which they in their turn give rise. Like their immediate progenitors, this offspring produce in their interior germ-cells which develop into minute worms having tails, and displaying great vivacity when placed in water. These latter alone exhibit the characters of true distomata. “These cercaria now either become enclosed, like a chrysalis in a pupa state, or they penetrate into the bodies of soft animals, become encysted and parasitic. It appears probable that the distomata enter the human intestinal canal as cercaria, and then pass into the biliary passages.”[260]
[260] Blyth.
A case is on record of two distomata having been extracted from the foot of a woman, into which it has been surmised they gained an entrance as cercaria whilst the woman was bathing.
It is thought that shell-fish, as well as uncooked fish when eaten, may be the means of introducing these parasites into the human system. The embryos of the Distomata hepaticum swim about and live in water, which may probably, when drunk, be the means of conveying them into the bodies of men and sheep. The ailments and symptoms to which these pests give rise depend upon the particular organ or portion of the body in which they establish themselves.
In man they are a frequent cause of hæmaturia and dysentery. In sheep they occasion fearful mortality, giving rise to the disease known as ‘the rot,’ and killing thousands of flocks annually.
“The number of species affecting men are usually enumerated as nine—viz. Fasciola hepatica, Distoma crassum, D. lanceolatum, D. ophthalmobium, D. heterophyes, Bilharzia hæmatopia, Tetrastoma renale, Hexathrydium renarum, and H. pinguicola.”[261]
[261] Blyth.
DISTORTIONS. In treating of this subject we shall confine ourselves to those distortions which are preventable—or rather, we may say, of two out of the three which will be discussed, which are voluntary.
One very common form of bodily distortion is crooked or curved spine. It is mostly met with in young girls of from ten to sixteen years of age; and first shows itself either in the elevation of one shoulder above the other, or in a growing out of one of the shoulder blades, or of one side of the bosom beyond the other. The elevated shoulder is generally the right one. At the same time the right side of the chest is unnaturally high, and rounded; whilst the opposite or left shoulder and chest are on the contrary depressed and concave. Very frequently these conditions are accompanied by a projection of the left hip, and a curving inwards of the loins on the right side. With persons so afflicted the spine presents an appearance that has not inaptly been compared to a long italic f.
Spinal curvature arises from a weakened state of the muscles, ligaments, and bones of the backbone. It is most frequently met with in those whose occupation compels them to stand the greater part of the day; as well as in persons who pass many hours at the desk or at needlework. Spinal curvature is also common in young fragile girls acting as nursemaids, and as such unduly subjected to carrying heavy infants on one side. Amongst the children of the poor, those of tender years are much too frequently put to this objectionable form of drudgery. Any one’s recollections of a walk through a poor neighbourhood will enable them to call to mind many instances they must have seen of smaller babes being nursed by larger ones. Those subjected to too long standing, no doubt because the posture affords them relief, unconsciously contract the habit of frequently standing on the right leg—of standing at ease on it, as it is called—and at the same time of bending the left knee a little; and since this position causes the right shoulder to be raised, and the left side of the pelvis to be thrown out of its place, it will be evident from what has been already said that, if persisted in, it will end in distorting the spine in the manner above indicated.