glands, nor did the glandular secretion come into immediate contact with the villi, but with the non-villous patches found on the chorion.

In the pig the villi were short, simple, and arranged on radiating ridges; in the mare they were filiform, and gathered into brush-like tufts separated by narrow non-villous intervals; in orca gladiator they were club-shaped, sometimes arranged in rows, sometimes in tufts. The shape and arrangement of the crypts on the surface of the mucosa corresponded to that of the villi in the chorion. In the mare they were distributed in areas which were separated by smooth ridges. On these ridges the glands opened. In orca the surface of the mucosa was irregularly divided by slight folds of membrane, and the crypts were distributed in the areas between these folds, but also in the folds themselves, and glands were found opening into crypts. The crypts were, however, far more numerous than the glands, and, consequently, there was a large number of crypts into which glands did not open, the mucosa of orca being more uniformly crypt-like than that of the pig or mare, so that there were no spaces free from crypts on which glands could open. According to the observations of Eschricht, however, who examined the gravid porpoise, the glands open in cetacea, not into the crypts, and the latter must be considered interglandular.

The epithelium lining the crypts in the pig was seen to be columnar; in the mare it was partly columnar, partly of an irregular shape, and partly hemispherical in form; in orca the epithelial cells had a transitional form between the cylindrical and tesselated varieties.

In all the forms of diffuse placenta examined the villi of the chorion did not enter into the glands, but into crypts which were formed on the mucous surface after impregnation; and the secretion of the glands did not come into immediate contact with the villi except in orca, when the glands opened, in some instances at least, into crypts. In all the others the crypts were interglandular.

The glands open on distinct spaces in the polycotyledonary placenta; the chorion villi are gathered into a number of tuft-like masses called foetal cotyledons. These are lodged in an equal number of crypts in the mucous membrane of the uterus -maternal cotyledons.

The cotyledons vary in shape and in number in different animals. In the sheep they appeared as "cup-shaped mounds" on the uterine wall. They consisted of a soft, spongy material, divided into numerous pits, were covered on the outer surface by mucous membrane and lined by cells of various shapes, some being cylindrical.

In the cow the cotyledons were fungiform, and connected to the mucosa uteri by a thick stem. The under surface was riddled with pits. In the deer the cotyledons were convex, as in the cow, but sessile. They were highly vascular, and in the connective tissue beneath the cotyledons of the sheep corkscrewlike arteries have been seen. The vessels in the cotyledon itself passed up to the surface in the connective tissue of the walls of the pits. They frequently branched and ultimately formed a capillary plexus, but did not dilate into sinuses.

The utricular glands did not open into the pits in the cotyledons, but on the intercotyledonary mucous surface. Gland openings were also seen on the outer mucous surface of the cotyledon of the sheep and on the stem of the cotyledon of the Cow. Glands were found, but not in great numbers, in the connective tissue beneath the cotyledons, but they appeared to be branches running obliquely, and not opening into the crypts of the cotyledon.

It has been supposed that the cotyledonary crypts of this form of placenta were the dilated mouths of glands, but it is almost universally agreed now that they are depressions formed after impregnation in the mucosa uteri.

The foetal cotyledons consisted of numerous vascular branching villi, which varied in shape and size according to the shape and size of the maternal cotyledons into which they entered. When the villi were withdrawn from the pits they carried with them some of the maternal epithelium, so that the polycotyledonary placenta is deciduate, while the diffuse variety is nondeciduate.

The zonary placenta is much more complex of structure than either the diffuse or polycotyledonary form. It is met with in the carnivora, pinnopedia, and some other animals. Professor Turner gives the following account of the naked-eye appearances of the pregnant uterus of a carnivora:

"The gravid uterus of the dog, cat, and other pluriparous carnivora possesses a moniliform appearance. Each dilatation is a compartment of the uterus containing an embryo with its membranes, and between adjacent compartments the uterine cavity forms a narrow tube. If one of these compartments be opened in a well-advanced stage of development of the embryo, the chorion will be seen to be smooth and bare of villi, except in about its middle third, where the villi are arranged as a zonular band around the transverse circumference of the chorion. The uterine mucosa possesses a similar zone closely blended with the zonular band of the chorion. The mucous membrane on each side of the zone is smooth and vascular; it lies in apposition with the smooth part of the chorion, but has no attachment to it. Where the zonary and smooth parts of the mucosa are continuous with each other a narrow strip of mucous membrane is reflected on

the margin of the zonular band of the chorion, and forms a rudimentary decidua reflexa."

In these lectures the zonary placenta is described as seen at some period of gestation in a considerable number of animals, but that of the cat is more fully described than any other, Indeed, the steps in the process of the formation of the placenta in this animal are traced from an early period of gestation up to the time of parturition.

At an early period of gestation in the cat the mucous membrane towards the poles of a compartment in which an ovum was lodged was smooth, and the placental area was marked by very delicate reticulations and studded with minute orifices. These were the mouths of the crypts within which the villi of the chorion were lodged. The surface was covered by short columnar epithelium. Glands were found in the connective tissue beneath the crypts, and were lined by columnar epithelium; but their orifices could not be traced. It was, however, ascertained that the crypts in a given area were much more numerous than the glands, and though some glands may open into crypts in the cat as in orca, yet the crypts must be considered interglandular. As development proceeds, the smooth patches at the poles of the chorion increase somewhat in size. The crypts become more dilated, deeper, and more subdivided, and the laminæ between them larger. The epithelium lining the crypts remained in part columnar, and in part had become "irregularly polygonal." The subepithelial connective tissue was vascular. Till nearly half the period of gestation had been completed the villi of the chorion could be easily separated from the crypts in the decidua; but about the half term this could no longer be done, and very important changes were found to have taken place. The villi were limited to the middle third of the chorion, and they were so interlocked with the corresponding zone of the decidua that the two parts of the placenta could not be disengaged from one another.

The villi passed almost vertically through the placenta up to its uterine surface, and the lamina of the maternal tissue forming the walls of the crypts passed between the villi, forming sheaths for their branches and stems up as far as the chorion. There was a well-defined decidua. The blood-vessels of the scrotina ramified throughout the lamina of the maternal placenta, and when injected they were seen to run up almost vertically to the foetal surface of the placenta, and the capillaries were "dilated to two or three times the size of the capillaries of the foetal villi," and near the foetal surface they dilated into sinus-like enlargements.

In the fox the dilatation of the capillaries was still more marked, and there can be little doubt that these dilated capillaries represented the maternal blood-sinuses which find their maximum development in the human placenta.

Thus it will be seen that the maternal part of the placenta in the cat and carnivora passes through the whole thickness of the organ as far as the chorion, that there is an intimate apposition of the surfaces of the chorion villi and of the maternal crypts, and that by this interlocking of the two parts of the placenta the foetal and maternal bloods are brought into near proximity. The maternal blood-vessels in some zonary placentæ are still covered by a stratum of connective tissue, as well as a layer of epithelial cells; but in the fox some of these vessels were found surrounded by a ring of epithelial cells only, the connective tissue stratum having become indistinguishable or having entirely disappeared. This condition will be seen in a more marked degree in still higher forms of placenta.

These lectures are of the greatest value as a contribution to our knowledge of the structure of the placenta. It is only by such studies in comparative anatomy that it is possible to unravel the structure of the human placenta. Not only is the latter organ at term of so complicated and so fragile a structure as almost to defy the inquiries of the anatomist, but it is fortunately also only very rarely that specimens of the organ in sitú can be found at term or at any other period of gestation; conse quently it has not yet been possible to trace month by mouth the steps by which the human placenta is formed from the earliest attachment of the villi to the maternal tissue till the organ is fully developed. In consequence of this it is necessary in this instance, as in many others, to call in comparative to explain human anatomy.

In this series of lectures the structure and mode of development of the simplest forms of placenta are deseribed; and we may infer with tolerable probability what goes on during the early period of gestation in the human subject. The course, however, is not yet complete. In his description Professor Turner has only reached that stage when the maternal capillaries have begun to enlarge; they have not yet become great sinuses, although traces of sinus-like dilatations were seen in some specimens of the zonary placenta. The further development of the placenta met with in the bell-shaped and discoidal varieties was described in a second series of lectures delivered at the Royal College of Surgeons in June last.

The series before us is illustrated by remarkably good coloured lithographs of sections of injected placenta and by some wood

cuts.

IV. Cerebral Physiology and Epilepsy.1

THAT the cerebral convolutions should have to do with special muscular movements and also with the processes of thought seems on its first announcement so strange a doctrine that the profession can scarcely be said, even yet, to recognise its true significance. It was easy enough to imagine that the convolutions had either function singly, but the alleged combination of spheres of action so different introduced an element of such confusion that few sought to overcome the difficulty involved in the proposition.

Many well-known facts in clinical medicine had indeed long pointed in this direction. For instance, it had become an aphorism, much insisted on by Dr. West, that "convulsions in the infant answer to delirium in the adult." Here then was a striking parallel drawn between muscular and mental perturbations. But perhaps nothing served to call attention so markedly to this subject as the elaborate study which has been made in recent years of cases of aphasia. This affection presents such a frequent combination of paralytic or convulsive muscular disturbance, with alterations in the power of speech, as to excite the most lively interest of physiologists and psychologists alike; this alteration in the power of speech is, moreover, found to vary in such a remarkable manner as to present nearly every gradation, from a purely paralytic affection of the muscles of articulation up to a complete loss of the intelligent recognition of words and of their voluntary use. Not only was aphasia found to be often associated with paralysis of the limbs, but when thus associated it was almost invariably the right side which was so affected; and from the pathological side, the lesion in the brain came to be localised with great certainty not only in the left side, but even in certain parts of the frontal convolutions. Thus we had a localised affection of the convolutions associated with special muscular disturbances in the right arm, and with mental disorder of such a special kind as almost to be limited to the use of words.

11. Clinical and Physiological Researches on the Nervous System (Reprints). No. I.-On the Localisation of Movements in the Brain. By J. HUGHLINGS JACKSON, M.D. London, 1875.

2. On the Scientific and Empirical Investigation of Epilepsies (being the introductory chapters of a forthcoming work on Epilepsy). By J. HUGHLINGS JACKSON, M.D. 'Medical Press and Circular,' 1874-1876.

3. Contribution à l'Etude des Convulsions et Paralysies liées aux MéningoEncephalites Fronto-pariétalis. Par LOUIS LANDOUZY. Paris, 1876.

4. Experiments on the Brain of Monkeys. By DAVID FERRIER, M.D. Proceedings of the Royal Society of London,' vol. xxiii. London, 1875,