tuting a nucleus. 12. The cells which are thus gradually formed out of the vitelline granules become joined together, and as their number increases, and they become pressed and flattened against the internal surface of the zona pellucida, they combine to form a delicate membrane, which lines the internal surface of the zona, and contains in its cavity a clear fluid which the ovum has gradually absorbed, and whereby it has become increased in size. The appearance therefore which the interior of the ovum presents in consequence of this new development is that of a vesicle, and it has been named accordingly germvesicle, or vesicula blastodermica (keimblase.) At one point of the germ-vesicle may be seen a round dark spot, which is called the area germinativa* (fruchthof;) in this spot the development of the embryo commences. On examining the ovum at this period with high magnifying powers, it may be seen that the yelk granules are arranged in concentric circles around the vesicle of the cells of the germ-vesicle. In proportion as the cells increase so the yelk-granules diminish in number, and finally disappear altogether. 13. As the ovum thus increases in size by the absorption of fluid into its interior, the zona pellucida surrounding it becomes greatly stretched, so that it loses its double contour, and is converted into a fine structureless membrane. But it still continues to act as the only external membrane of the ovum; for even in the uterus there is no deposit of albumen around the zona. 14. The ovum, therefore, at the commencement of its stay in the uterus, is composed of two pellucid vesicles inclosed one within the other, and closely joined together-the zona pellucida and the germ-vesicle, or vesicula blastodermica; within the latter is situated the area germinativa, or spot where the formation of the embryo commences. At this time the ovum lies free in the uterus, and gradually makes its way to the spot where it will eventually become fixed. The power which determines the part of the uterus at which the ovum shall settle is quite unknown; it does not appear to depend on anything in the organization of the uterus itself.— Sometimes the ovum, when arrived at the uterus, passes across its cavity, and attaches itself at the side opposite to that at which it had entered. 15. When the ovum has attained the size of from one and a half to two Paris lines, a close examination will find that from the internal surface of the vesicula blastodermica, at the point where the area germinativa is situated, a second delicate cellular layer has formed, so that the vesicula germinativa now consists of two membranes, the external of which is called the animal layer, the internal the regetative. They are so designated because at the part of the area germinativa which corresponds to the external layer the organs of animal life are formed in the embryo, whilst at the part adjoining the internal layer the organs of vegetative life are formed. Between these two layers there, probably in a short time, is formed a third, in which the blood-vessels are developed, and which may therefore be called the vascular layer. It is only at a later period, however, that this third layer can be clearly demonstrated. 16. Until the 20th or 21st day post coitu the area germinativa has consisted merely of a dark accumulation of cells, but it now begins to brighten in its centre, and to be divided into two parts, a bright central portion (the area pellucida) and a dark circumferential part (the area opaca.) The earliest trace of the embryo commences in the area pellucida, and consists at first of an elliptical, then of a guitar-shaped heap of cells situated in the animal layer, in the long axis of which heap a bright streak may be observed. In the accumulation of formative matter on either side of this bright streak are formed the walls of the body of the embryo. The portions of this formation immediately adjoining the streak are called the lamina dorsales, and the portions external to these, the lamina abdominales, or visceral plates. The longitudinal streak itself is called the primitive groove. The first trace of the embryo therefore consists of two seperate halves. 17. In the primitive groove are formed the central parts of the nervous system, namely, the brain and the spinal cord.—

* These terms are used by Mr. Wharton Jones in his Report.

Neither of these two arises from the other, but each has its own separate development. 18. After the formation of the central parts of the nervous system, the heart and vascular system are next developed. Here again also the heart is not formed out of the blood-vessels, neither do the arteries and veins originate from the heart, but each is developed separately and independently of the other. Finally, is developed from the central part of the vegetative layer of the vesicula blastodermica the intestinal system, namely, the intestines, lungs, liver, pancreas, &c. 19. The mode in which these systems and the organs belonging to them are formed in the ovum of the bitch, is exactly similar to that which takes place in other mammalia and in birds. The development of these parts proceeds so rapidly when once the first trace of the embryo appears, that after forty-eight hours the three chief systems are laid down.

3.-On the Relation between the Constituents of the Food and the Systems of Animals. By R. D. THOMSON, M. D., &c. &c.

The first individual who showed that wholesome food should contain matters identical with animal substances was Beccaria, of Bologna, who wrote an excellent paper on the subject in 1742. Dr. Prout has taught and extended this view for more than twenty years, and his opinions are now followed by all physiologists. That the systems of animals are capable of sustentation by a supply of fibrinous matter alone, is obvious from the history of the primitive inhabitants of the prairies of America; but it appears from experiments made on the nutrition of animals with pure fibrin, that an auxiliary in the production of animal heat is either indispensable or advantageous, since animals fed on fibrin alone invariably declined in health. (Magendie.) That the amount of calorifient, or heat-producing food, in contradistinction to nutritive food, properly so called, as it has been well defined by Liebig, is out of all proportion greater than that required to supply the waste of solid matter of the body, is obvious from an experiment made by the author on a cow, in a state of rest, in which it was found that 15 lbs. of food were taken into the circulation in one day. Of this, only 14 lbs. was nitrogenous or nutritive food; the rest being calorifient and saline. From this experiment, frequently repeated with nearly the same results, the author concludes that in such a condition of the system, the natural relation of the nutritive to the calorifient constituents is nearly as one to eight one-third. The author gives formulæ for calculating the amount of nutritive and calorifient food, with a view to determine the laws of dieting.He also gives tables from his own analyses, of the amount of nutritive matter in about twenty different kinds of vegetables (principally farinaceous food.) By these it is shown that oatmeal consists of 1 nutritive and 5 calorifient matter, and barley 1 and 7-facts which explain the universal employment of these substances. From these tables it is also inferred, that as milk is the natural food of the infant mammalia, the constitution of their food should be formed on the same type, and that of the use of arrow-root or starchy food, where the relation of the nutritive to the calorifient matter is as 1 to 26, instead of being as in milk 1 to 2, is opposed to the principles attempted to be established by the author. He observes that, in nutritive tables, it is usual to give a column of equivalents-representing, for example, 100 parts of beans as equal in nutritive power to 1160 of starch; but, according to the author's views, such a method is not founded on scientific principles. In a correct plan of dieting, a proper equilibrium must be maintained between the wants of the animal organism and the constitution of the food. The importance of this view is supported by the results of an extensive series of experiments, made by the author with different kinds of food upon cows. These results are highly interesting, and were given in a tabular form, but our limits will not allow us to detail them at length.

The author concludes by observing that, when more condensed forms of vegetable are required, the object might be obtained by mixing certain portions of

American flour with different kinds of meal, which could not otherwise be raised by fermentation; for example, by mixing equal parts of flour and oatmeal, flour and peas or barley meal, excellent bread could be formed; and two-thirds of Indian corn with one-third of flour yielded an excellent loaf.

Dr. Golding Bird, while he bore testimony to the industry and patient investigation which characterized the researches of Dr. Thomson, could not agree, in the conclusions at which he had arrived with reference to the dietary of persons in health and disease. It should be recollected, that previous to the labours of Liebig, the proportion of carbon which existed in various articles of food was thought to offer a fair indication of their nutritive power. That distinguished philosopher, however, had shown the fallacy of such a view, and had proved that, with the exception simply of the fatty tissues, every structure in the body was supported, and its waste supplied, by the nitrogenized elements of food.— Dr. Thomson's paper had the merit of satisfactorily showing that animals could not be well nourished on nitrogenized or carbonized food by itself, but that there should be a certain proportion between the two, so that the richly-nitrogized food might make up the waste of tissue, whilst the richly-carbonized would become a source of animal heat. He (Dr. Bird) did not believe that the composition of the food of the infant animal, or milk, gave us any sure indication, in our selection of nutriment for the adult; for milk, nearly identical in composition, afforded nourishment to the infant cat, sheep, and porpoise; whilst, in after-life, how remarkably different was the food of these different animals.

Admitting that the tables of Dr. Thomson were correct, it would seem that the most nutricious food for infants and invalids, next to milk, would be beans and peas. This could not be followed out practically. White bread, according to the tables, was below beans and peas in nutricious power; but, trusting to the same authority, a portion of cheese added to it would, theoretically, raise it high in the scale of nutriments: yet who would carry out this view practically? He admitted that infants might be literally starved from eating arrow-root, in consequence of their supply of nitrogen being cut off; he yet believed that in these inquiries sometimes more than the mere chemical principles must be taken into the account in our determination of the diet we shall select for our patients. The ease with which different kinds of food were digested, and the vital endowments of the stomach, must not be overlooked.

Dr. Babington observed that the last speaker had gone much too far in his criticism, as every one must be aware that animal food and some other kinds of condensed nitrogenous matter might not be suited to children, from their difficulty of digestion. He considered the paper a very valuable one, and deserving of the thanks of the society.

[Although one of the speakers stated that there was not much novelty in the views brought before the society by Dr. Thomson, we confess that to us, and to all with whom we have conversed on the subject, many of the facts and deductions are quite original. The table, which exhibited an increase in the butter of the milk of the cow, in proportion to the augmentation of nitrogen in the food, is perfectly new, and apparently at variance with the theories of Liebig, who derives the butter from the starchy constituents of the food; but which Dr. Thomson reconciled, by considering the food in these cases to be so formed as to restore the proper equilibrium of the system of the animal. This view also leads to the novel suggestion, that by experiment we should determine the amount of matter removed from the system under different circumstances of rest and exercise, and that a true plan of dieting should be founded on such knowledge, and should not be left to mere instinct. We believe with Dr. Thomson, that on this consideration depend the true laws of dieting-a subject of so much the greater interest in an artificial state of society, where the food is too frequently concocted to minister to the palate instead of to the condition of the waste of the system. The relation which Dr. Thomson instituted between the food serving for nutrition and that for the mere production of animal heat was very striking, and we have certainly never seen the subject so treated

before. This analysis of arrow-root, tapioca, and sago, was also quite new, and demonstrated the impropriety of employing them as food for children. The table, already alluded to, showed, contrary to the statement of one of the speakers, that arrow-root could not produce fat, and that such views are imaginary. The table containing the amount of albuminous matter in various kinds of vegetable food, was highly important. The higher position occupied by Scottish oats and barley-meal over English flour is a new and startling statement. We concur in the concluding observation in Dr. Thomson's paper, that his remarks tend towards an extensive field of experiment and deduction, of a highly practical nature, and may assist in indicating the direction in which the physician should pursue his inquiries when studying the laws by which the animal system is to be retained in a state of health.-Reporter of the Gazette.]

Med. Gaz., May, 29, 1846, p. 965.

Part Fourth.

MEDICAL INTELLIGENCE.

FOREIGN.

(By reference to the papers of Drs. Hicks and White, in our first part, it will be seen that this fatal disease has made its appearance in the valley of the Mississippi.)

1-Epidemic Cerebro-spinal Meningitis.-The disease of which an account, as given by Dr. Darby, is mentioned in our last volume, p. 75, has more recently been noticed by Dr. Mayne, who witnessed it in the Irish workhouse to which he is medical attendant. The pathology of the disease as described by him appears to have been uniformly the same in all the cases examined.

"In the post-mortem examinations which have fallen under Dr. Mayne's notice, the scalp and dura mater exhibited but little undue vascularity; the pia mater covering the hemispheres of the brain was congested, and the large veins, in their way to the several sinuses, appeared remarkably turgid. The free surface of the cranial arachnoid felt dry and clammy, and had lost its transparency in many places, particularly at the base of the brain; but there was no lymph or other inflammatory effusion in the sac of the arachnoid. Lymph of a yellowish or greenish hue appeared on the surface of the encephalon beneath the serous tunic; this occurred sparingly on the upper surfaces of the hemispheres, and there only along the sulci, but at the base of the brain it was found in greater quantities, especially in the sub-arachnoid space corresponding to the circle of Willis, where many of the cerebral nerves at their origin were fairly imbedded in it. In the spinal canal a similar exudation filled the sub-arachnoid space; it there existed in sufficient abundance to envelop the cord completely; it also extended down to the lowest extremity of the cauda equina, investing each of the spinal nerves at its source; but in the vertebral canal, just as in the cranium, the cavity of the arachnoid contained none of this morbid secretion. The substance of the brain and spinal marrow appeared remarkably free from lesion; there was no unusual vascularity, induration, or softening apparent, nor did the ventricles betray any evidence of inflammation. A remarkable feature of this malady is the class of persons on whom it has seized. In Ireland, so far as has been ascertained, boys under twelve years of age have been, with few exceptions, its only victims; the seven cases reported by Dr. Darby were all boys, and only one of them had passed his twelfth year; in Belfast ten cases of the disease were noted, all occurring in boys from seven to twelve years of age; and in Dr. Mayne's experience, individuals of the same description have alone

* Dublin Journal, and Med. Times.