worms, or Sterelmintha—repeos, solid, and Exps. Such of the parasites as I have already described are also arranged by some authors under one or other of these heads, but the distinction with them is of secondary importance. In the first class we have, 1. The Tricocephalus Dispar, or long thread-worm, usually found in the cœcum and large intestines, measuring about two inches in length, and having a very slender body. It is often found in considerable numbers, even in the intestines of healthy persons; during life they give rise to no symptoms. 2. The Ascaris Lumbricoides, or large round-worm, is found in the small intestines, especially of ill-fed children. It somewhat resembles in size the common earth-worm, varies in length from six to nine inches, and is of a light yellow color. The symptoms which it gives rise to are thirst, disturbed sleep with grinding of the teeth, pallid countenance, fœtid breath, swelled belly, emaciated extremities, depraved appetite, slimy stools, itching of the nose, tenesmus, and itching of the anus. 3. The Ascaris Vermicularis, or small thread-worm, is found in the rectum, and is the smallest of the intestinal worms, averaging usually about a quarter of an inch in length. It gives rise to intolerable itching and irritation about the anus, tenesmus, depraved appetite, picking of the nose, depraved breath, and disturbed sleep. In the second class we find, 1. The Tania Solium, or common tape-worm of this country, which exists in the small intestines, varying in length from five to ten feet, and in breadth from one line-at its narrowest part -to four or five at its central or broadest portion. The head of this parasite is small and flattened, having in its centre a projecting papilla armed with a double circle of hooks, around which are four suckers or mouths, by which nourishment is imbibed; the generative apparatus consists of a ramified canal or ovarium containing the ova, and occupying the centre of each joint. The symptoms of its presence are not very striking, its existence being generally unsuspected until single joints are passed in the stools; in many cases, however, there is a continual craving for food, debility, pain in the stomach, emaciation, and itching about the nose and anus. 2. The Bothriocephalus Latus, or broad tape-worm is almost peculiar to the inhabitants of Switzerland, Russia, and Poland. It differs from the common tape-worm in having its segments of a greater breadth than length. The extreme fertility of the bothriocephalus latus may be understood by considering that each foot of the well-developed worm contains 150 segments or joints, each joint possessing its own ovary and male organs. Hence each joint is fertile, and as each ovary would produce 8000 ova, it may be calculated that ten feet of such a worm would produce 12,000,000 of ova. They are very rarely met with in this country, but they are so occasionally. Professor Owen, examining the collection of a worm doctor in Long Acre, found three specimens; two had come from persons who had been in Switzerland, but of the third nothing was known. 2. EXTERNAL PARASITIC WORMS. The Pulex Penetrans, or Chigoe.-This small insect is found in America and the Antilles; it penetrates the epidermis, and there lodges its eggs to about the number of sixty, which, when hatched, create great irritation, and often serious mischief. The native inhabitants extract them very skilfully with a needle, taking care not to rupture the cyst in which they are inclosed. The Acarus Scabiei.-This little parasite, belonging to the class Arachnida (spiders) of articulated animals, is now generally admitted to be the cause of that loathsome, conta. gious disease of the skin-scabies. It is generally found about a line from, but not in, each vesicle. M. Bourguignon's researches on the nature and habits of the acarus scabiei show that the male is but one-third of the size of the female; that he is the most nimble of the two, being very lively when the body is warm; and that he is the least frequently met with. He has suckers on two of his hind feet, and genital organs on the surface of the abdomen. The female burrows into the epidermis, and lays four eggs at intervals of about four days between each deposit, shifting her position in the meantime until sixteen eggs are inserted beneath the skin. In ten days the shells are broken, and the insects make their appearance as six-legged larvæ, increase rapidly in size for a few days, then shed the shell-like the crustacea-and acquire eight legs, when they are perfectly developed, and capable of tormenting man and reproducing their species. The males and young females do not burrow into the epidermis as the pregnant females do, but run about on the surface, puncturing the skin merely for blood-globules and serum, on which they live. The Acarus Folliculorum.-The acarus folliculorum, or the steatozoon folliculorum,' was discovered by Dr. Simon, of Berlin, in the sebaceous substance with which the hair-follicles -especially those on the face-are commonly filled. It is very minute in size, measuring little more than a quarter of a line in length, and being undistinguishable by the naked eye; it is divisible into a head, thorax, and abdomen, and resembles in form and shape the common caterpillar. This animalcule is found in numbers varying from one to twenty in the sebaceous follicles or oil-tubes of the skin in the majority of mankind, and always when any disposition exists to the unnatural accumulation of sebaceous matter: the skin at the same time is apparently healthy. They may be obtained by compressing the skin until the sebaceous matter is squeezed out: a microscope magnifying 250 diameters will detect them. Mr. Erasmus Wilson regards these steatozoons as performing a beneficent purpose in the economy of the skin, that purpose being the disintegration of the over-distended cells, and the stimulation of the tubes to perform their office more efficiently. Pediculi.—The human body is infested with four different species of the pediculus, or louse-of which the pediculus capitis, or louse of the head, is the most common; next, the pedi culis pubis, or crab-louse, which attaches itself to the hair about the pubes and anus; the pediculus corporis, or body louse, often found in the clothes; and, lastly, the pediculus ciliorum, or louse of the eyelash, which is very rare. CHAPTER XI. ON THE CHEMICAL AND MICROSCOPICAL EXAMINATION OF THE BLOOD, EXPECTORATION, VOMITED MATTERS, AND URINE. Ir was my original intention to devote this chapter to a full consideration of all the secretions and excretions of the human body; but want of space compels me to limit myself to the examination of the blood, sputa, vomited matters, and urine. I may, however, observe that the chief excretions consist of the watery vapor and carbonic acid exhaled by the lungs; the sweat, excreted by the skin, consisting chiefly of watery vapor, lactic acid, a small quantity of carbonic acid, a little oily matter, and a small proportion of the same animal and saline matters as are contained in the blood; the excretions from the bowels, i Wilson, on "Diseases of the Skin," p. 466. including the bile; and, lastly, the most complex of all the excretions-the urine. The retention of any of these excretions in the body is most injurious, and often fatal, since the peculiar matters characterizing them are not formed from the blood, but actually separated from it, at the parts where they appear; allow, therefore, these excrementitious matters to accumulate in the circulating fluid, and general constitutional disturbance must result. This is well seen when the principles of the bile remain unseparated from the blood, owing to defective secretion on the part of the liver, and jaundice results; or, to take another example, when, owing to severe renal disease, the urea, instead of being removed by the kidneys from the circulating fluid, accumulates in it, and actually poisons the sufferer. SECTION 1. THE BLOOD. The general appearance of the blood is familiar to every one it is slightly alkaline; has a faint odor; a saline disagreeable taste; and a higher specific gravity than any other animal fluid-averaging 1050 or 1055. When circulating in the vessels, blood is composed of a nearly colorless, transparent liquid-the liquor sanguinis-in which numberless minute disk-shaped bodies or corpuscles are suspended or floating. The liquor sanguinis consists of water, fibrin, serum holding albumen in solution, certain extractive and fatty matters, and fixed saline matters. The blood-corpuscles-usually forming about 130 parts in every 1000 of healthy blood-are of two kinds; the red corpuscles, by far the most numerous, to which the red color of the blood is due, about the both of an inch in diameter, consist of membranous vesicles filled with red fluid, which fluid is composed of coloring matter containing iron-termed hæmatin, and of a protein compound, somewhat analogous to albumen, called globulin; and the white corpuscles, somewhat larger than the red ones, about the both of an inch in diameter, irregular in form, slightly granular on the surface, and apparently identical with the peculiar corpuscles found in the lymph and chyle. On removing blood from the vessels, and allowing it to repose for a short time, it coagulates-that is to say, the liquor sanguinis separates into two portions: the colored clot or crassamentum-consisting of the fibrin and blood-corpuscles, and the fluid portion, consisting of the serum holding the albuminous and saline matters in solution. The formation of the clot is owing to the solidification of the fibrin, which, while becoming solid, entangles the red and white blood-corpuscles in its meshes. In certain states of the system, when the fibrin coagulates more slowly, or when the corpuscles sink more rapidly than in healthy blood, the upper surface of the clot will be colorless, presenting an appearance known as "the buffy coat," which was formerly thought to be indicative of inflammation. Occasionally this buffy coat, when the blood is rich in fibrin, is depressed in its centre, and the blood is then said to be "cupped and buffed." Chemical Composition of Human Blood.-To make a complete quantitative analysis of the blood, including the separation from each other and estimation of all the ingredients, is a complicated and difficult task, and requires the person undertaking it to be a good chemist. Such an analysis is, however, quite unnecessary for clinical purposes, although it is as well that the result of such an examination should be roughly remembered. I shall therefore quote the following table by Dumas: Analysis of Healthy Venous Blood. Globules, {Hæmatin, 130 Clot, Globulin, Water, Albumen, 3 2 125 790 70 Arterial Blood merely differs from venous in containing less solid matter, less albumen, less salts, and in being of a bright scarlet color, which latter is probably due to the influence of the oxygen of the air. In anæmia and chlorosis the water is sometimes increased to 900 parts in 1000, and the globules diminished even to as low as 21 in 1000. In fever the globules have been known to amount to 185 in 1000; while in |