Taxodium distichum, (Cypress tree.) This truly valuable timber tree is met with abundantly in the lakes and lagoons of all the counties bordering on the Ohio river, in the West of Kentucky; where the peculiar excrescences called "Cypress Knees" form obstacles in the way of crossing the water-courses.

Verbena spuria, roadsides in the barrens, in common with V. angustifolia.

Wistaria frutescens. A flowering pea-vine, now common in gardens and shrubberies; abundant on the banks of Little River in the West of Kentucky.

Xanthium spinosum. A pestiferous species of cockle-bur, which, it is to be feared, will become extensively naturalized. As yet, I have only met with it on the commons of Portland, below the falls of the Ohio.

Yucca filamentosa, (Adam's thread, Bear-grass, &c.) A showy and ornamental plant, frequent in gardens; and which I am informed by the Rev. Mr. Jones, of Hopkinsville, grows abundantly on the Cumberland mountains, in the S. E. corner of Kentucky. An opinion is entertained by some, that the stream which enters the Ohio River at Louisville, derives its its name from this plant, which is supposed to have once grown on its banks. This is most probably erroneous; and it is more likely that the name of the creek was taken from some of those rank and luxuriant grasses, so common in similar alluvions, as Panicum crus-galli, and others.

August, 1840.

REVIEWS.

(Continued from the September number.)

ART. III.—Elements of Pathological Anatomy; illustrated by numerous engravings. By SAMUEL D. GROSS, M. D. Boston: 1839.

THE notices of some of the first chapters this book contained in our last number were a part of the article published in the preceding, the limits of which did not permit an insertion of the whole. The division was made in the absence of the Reviewer, and the article appeared, therefore, without exordium or peroration. With this explanation we proceed to the analysis of other portions of this comprehensive work.

The 15th chapter treats of hydatids. We agree with our author when he affirms, that most American physicians are unacquainted with this subject. It is but justice, however, to add, that, curious and interesting in a physiological and zoological point of view, as these productions may be, their study by the practical physician, is not of very great importance. This results, first from the rarity of hydatids in the human body; and second, from the impossibility in most cases of relieving the patient, when they are known to exist. Nevertheless, every physician ought to have a general knowledge of this class of beings; and such a knowledge can be succesfully acquired in a single hour by the study of the dozen pages which our author has devoted to them.

"Hydatids occur in serous cavities, the alimentary canal and the passages which open into it, the cellular tissue, between the muscles, and in the proper substance of the different organs. Nevertheless, there are, as will be seen hereafter, some parts that are more frequently affected than others. They have been found in nearly all classes of animals,-in birds, reptiles, and fishes, as well as in a great many of the mammalia. Whether they exist in insects, is a point which has not been ascertained. No period of life is exempt from them. Portal, indeed, mentions an instance of their having been detected in the foetus. They are most common, however, in adults and old people.

"So far as can be ascertained, these parasitic beings possess no genital organs, no apparatus for respiration, no trace of a circulation, and apparently no nerves. They can live and propagate their species only in the interior of other animals, and their existence is usually very brief, most of them perishing within the first year or two after they are developed, often much earlier. A few of them only are capable of performing distinct movements, under the influence of external stimulants. The cysticercus, for example, when put in luke-warm water, not only whirls itself about, but alternately protudes and retracts its suckers. The acephalocyst, on the contrary, remains perfectly quiescent, and may therefore be said to be void of irritability and contractility."

Hydatids are naturally divisible into two great classes— the cephalocysts, or those in which a head is associated with the cyst, and acephalocysts, or those in which there is no appearance of such an organ or any other. Of the former our author describes and figures four genera: 1st. The cysticercus, or bladder-tailed hydatid, of which he enumerates, with Cloquet, five species; most of which have been found but a single time in the human body, all of them in the plexus choroides and some of them there only. In our domestic animals, as the hog, sheep, ox, and goat, they are more common. 2d. The polycephalus, or many-headed hydatid, not yet found in man. 3d. The diceras, or two-headed hydatid, observed, once, to have been discharged from the human

bowels. 4th. The echinococcus, or rough hydatid, found a single time in the brain, and discharged once from the bladder.

From this enumeration it will be perceived, that the cephalocystic hydatids do not present themselves often enough in the human subject to be of much interest. Their greater frequency, in our domestic animals, constitutes them legitimate objects of epizootic medicine.

The other great class, acephalocysts, are much more common in the human body, and therefore more deserving of notice.

"Occurring both in the human subject and in many of the inferior animals, the individuals of this class of parasites infest some organs much more frequently than others. They seem to have a remarkable predilection for the liver, owing, probably, to some peculiarity of structure favoring their development. The brain, ovary, uterus, mammary gland, spleen, and kidney, are also sometimes their seat; in fact, they have been found in every part of the body, except the alimentary canal, the urinary bladder, and the respiratory passages.

"Varying in size between a mustard-seed and a large orange, they are generally of a spherical figure, and composed of a white, semi-opaque, pulpy vesicle, filled with a clear, limpid fluid. This vesicle, which forms the hydatid, properly so called, is from the sixth of a line to the eighth of an inch in thickness, and is often separable into two or more layers, and is so exceedingly delicate as to yield under the slightest pressure of the finger. So weak is it, indeed, that it is frequently incapable of withstanding the pressure of its own contents, as I have had repeated opportunities of witnessing, after the partial removal of the enclosing cyst. On being ruptured, it shrinks up into a soft, irregular, pulpy mass, of an opaline color, which readily swims in water, and bears the greatest resemblance to coagulated white of egg.

"It sometimes happens, though not very often, that a large acephalocyst contains several that are smaller, one within the other, all of the same shape and structure. As many as three, four, and even five, have been found thus enclosed, like so many pill-boxes. This arrangement, which occurs much oftener in the human subject than in the inferior animals, is

explained by the endogenous mode of generation previously adverted to, by which one acephalocyst, after having arrived at maturity, produces another, each successive one being smaller than its parent."

Our author like most of his predecessors indulges but little in speculations on the origin of hydatids; yet true to the theory, that most morbid products are the result of inflammatory action he strongly inclines to that view of their origin. In speaking of the causes which develope acephalocysts, he remarks:

"In Cincinnati, where there are annually slaughtered upwards of one hundred thousand hogs, probably not a tenth part are free from this disease. Whole droves, consisting of three or four hundred head, are sometimes thus affected. These animals, most of which are young, are raised in the prairie districts of Ohio, Indiana and Kentucky, and are literally stuffed, for six or eight weeks before being sent to market, with fresh corn. The consequence is, that the portal circle is kept in a state of constant congestion, which finally leads to inflammatory irritation and the development of acephalocysts in the liver and other viscera. The irritation thus set up is of a specific nature, and is followed by the deposition of a fibro-albuminous substance, or, what is the same thing, a sort of plastic lymph, the particles of which arrange themselves in such a manner as to create an inferior being, an entozoic parasite."

Undoubtedly, the great hydatid development in these cases is connected with an increase in the diet of the animal, originating a very active and nutritive process, particularly the adipous system; but we do not admit, that such a condition is necessarily attended with inflammation. In fact, we generally find, that individuals who generate great quantities of fat are less than others inclined to the phlegmasiæ, for the secretion of so much fat keeps down plethora. But if excess of nourishment generates hydatids by exciting inflammatory action, how does it happen, as we state in the words of our