At the age of eleven years the cartilaginous canals were found to be still diminishing both in point of size and number; and in the examinations made at seventeen years, it was with great difficulty that a section could be found in which there was any remaining trace of them. Sections taken from the cartilages and ossifying extremities of the bones of the slink or foetal calf, were examined in the microscope. The cartilaginous canals were found to be very numerous. They were all filled with a clear mucilage, and the sides of the canals in many parts of the cartilage had the appearance of being stained with blood, although no distinction of blood-vessels could be detected in any of them. By a series of these examinations it was ascertained, that the cartilages upon which the flat bones of the scapula and ilium are produced, possess a similar organization to that which obtains in the cylindrical bones. The posterior extremities were injected with coloured size, and the cartilage then examined in sections, under the microscope. The membranes covering the cartilages and bones externally were beautifully injected; the canals within the cartilage also were equally well injected. Wherever the canals appeared, they were observed to have received the vermillion. Several oblique sections of canals fell under observation, and in those a membranous lining was very readily discerned, the injected state of the parts rendering the divided edge of the membranous tube very obvious. In some instances this membrane became still more evident, by its having been partially separated from the divided edge of the canal. Where the canals were found to be divided longitudinally, the membranous lining was, in general, still attached to the sides of the tube, and the beautiful appearance of the injected membrane, was rendered still more brilliant by the abundance and crystalline transparency of its natural mucous secretion, In many parts of the cartilage where the lining of the canals was finely injected, there was still no appearance of distinct vessels, although in those canals that were opened at their origin upon the external surface of the cartilage, a dis tinct artery, full of the injected matter, might generally be traced, passing inwards to some extent. In the more internal canals, the usual appearance of the membranous sheath, under the microscope, was such as it would have been if the injection had passed out from the vessels, and become dispersed in the cellular texture of a fine membrane; had so peculiar an appearance arisen from the accidental rupture of the coats of the arteries, the injected matter must have been detected in masses, which was not in any instance the case. In those canals that were divided obliquely, the finely and equally injected membrane had the appearance of an uniformly scarlet tube; and by increasing the magnifying power to a very high degree, the individual particles of the vermillion not only became visible, but were seen most distinctly; they were every where found to be very thinly and evenly scattered, indicating the most equal dispersion of the colouring matter throughout every part of the membrane, In prosecuting this part of the inquiry, a considerable difficulty at first arose out of the following circumstance. The heat of the water, in which the preparation was laid previous to its being injected, had so far loosened the membranes from the sides of the canals, that in the subsequent operation of dividing the cartilage into sections, they were torn from their natural situation, and were consequently found in many parts more or less collapsed. These collapsed membranes had, under the microscope, very much the appearance of injected arteries, and were at first considered as such, but subsequent and more attentive observation soon enabled me to correct this mistake. From the foregoing observations I think myself warranted in drawing the following conclusions. 1. That, in the mammalia, the first rudiments of ossification in the long bones are the effect of a secreting power in the arteries, upon the internal surface of the periosteum, which produce a portion of a hollow cylinder; this form of bone having been found antecedent to the evolution of any cartilaginous structure. 2. That, at a certain stage of the process, the mode of operating is changed, in order that it may proceed more expeditiously. A cartilage is formed, which, by the nature of its organization, and by admitting of a specific provision of cavities and canals, lined with vascular membranes, which secrete an abundant store of gelatinous matter, is adapted to this particular purpose; while, at the same time, it serves to determine the future figure of the extremity of the bone, by establishing and conducting the ossification within its own substance. 3. That, from the appearance and texture of cartilage, when examined under the microscope, it may be definedan even and finely granulated albuminous matter, deposited in the interstitial spaces of an exceedingly elastic bed of a semi-transparent reticulated structure, which is apparently a modification of gelatin. 4. That from the period when the ossification proceeds in the mode above described, by the medium of cartilage, the process is continued in the same uniform manner till it has completed the growth of the bone. The growth of the epiphyses and their union with the ends of the bone, are also effected by the same means. 5. That the ossific matter in the cylindrical bones is deposited primarily in the form of fine thin tubular plates; a mode of deposition of all others the most favourable for their being subsequently remodelled, and for facilitating all the subsequent changes of structure they are destined to undergo. 6. That, while the circulation in the capillary arteries, situated between the cartilage and bone, must provide the phosphate of lime, the principal agent in extending the cylinder, and in effecting the subsequent progressive changes of structure, which, in a growing bone, are continually taking place, appears to be simply the mechanical pressure exerted by the fluid secretions within the medullary cavities of bone, this power operating successively in different directions, according to the particular determination given by the circulation. 7. That the mode of circulation most favourable for ossific action, is a very slow and uniform motion of the blood through the capillary system; and that the numerous inflexions of the minute arteries, in the pericranium, and the great weakness and rectangular mode of giving off the smaller arteries upon the dura matter, as well as the extremely curious appearance of the blood and injected matter, upon the fine membranous Jinings of the canals in cartilage, indicating, as I believe, something beyond a mere capillary circulation, are to be considered as so many evident provisions for securing this condition. 8. That in the formation of the cylindrical bones, the ossific surface is arranged into tubular plates of two different sizes, constituting a larger and a smaller series; an arrangement by no means essential to the increase of a bone, because in many of the early stages of ossification, and also where the growth is very slow, the larger series is found to be entirely wanting. 9. That the only apparent use of the larger series of tubes, is that of augmenting the quantity of blood circulated through the ossifying structure, so as to increase the rapidity of growth, for they are abundant in animals of quick growth, less numerous in those that reach maturity slowly, and in the same animal I have observed they are employed by nature, or laid aside in conformity with the quick or slow developement of structure, which we know actually takes place at the particular period when the examination is made. 10. That in the growth of the cylindrical bones, and of those flat bones that are formed upon cartilage, the deposit of the ossific secretion is in the first instance made around the external openings of the smaller series of tubes, and upon these only. This opinion derives support from the recent appearance of the bones of quadrupeds, but is most clearly established by the characters found upon the ossific surface in the bones of birds, where the gradations of progressive evolution are more readily traced. 11. That in the flat bones of the skull, the circumstances under which ossification takes place, differ materially from those above described. In these the phosphate of lime, in combination with the animal mucilage, is occasionally deposited in small detached unequal masses, without regularity, as if merely laid in the way preparatory to their subsequent application; that these soon become connected with the more central parts of the bone, and are found to decrease in thickness as they increase in breadth, until they are finally consolidated with the original plate of bone. 12. That the particular simplicity observable in the mode of production of the bones of the skull, affords a strong argument in favour of the opinion, that pressure, variously modified, constitutes one of the most efficient instruments in the hand of nature; for in this instance, the uniform, though gentle pressure from the impulse of the circulation, and the constantly increasing volume of contents in the head, must be admitted to be the sole agents in completing that process, which, in its commencement, had the appearance of being conducted in a comparatively imperfect manner. 13. That the ultimate texture of bone is not laminated, but reticulated, the phosphate of lime being deposited as an intestinal substance; for, although, from the greater compactness necessary to the bones of quadrupeds, the ultimate structure is not in them so readily traced, yet in the more delicately constructed bones of birds, this mode of arrange. ment is sufficiently obvious, and may at any time be readily ascertained. Like leaves on trees, the race of man is found; Now green in youth, now withering on the ground. So flourish these, when those are past away. POPE. Efficacy of Water in the Growth of Vegetables. 198. That vegetables will grow in woollen cloth, moss, and in other insoluble media, besides soils, provided they be supplied with water, has been repeatedly shown since the days of Van Helmont and Boyle: but the experiments of a modern author, from their apparent correctness, seem more highly interesting and conclusive. Seeds of various plants were sown in pure river-sand, in litharge, in flowers of sulphur, and even among metal, or common leaden shot; and in every instance nothing_employed for their nourishment but distilled water. The plants throve, and passed through all the usual gradations of growth to perfect maturity. The author then proceeded to gather the entire produce, the roots, stems, leaves, pods, seeds, &c. These were accurately weighed, dried, and again weighed, then submitted to distillation, incineration, lixiviation, and the other ordinary means used in a careful analysis. Thus he obtained from these vegetables all the materials peculiar to each individual species, precisely as if it had been cultivated in a natural soil,-viz. the various earths, the alkalies, acids, metals, carbon, sulphur, phosphorus, nitrogen, &c. He concludes this very important paper nearly in these extraordinary words: "Oxygen and hydrogen, with the assistance of solar light, appear to be the only elementary substances employed in the constitution of the whole universe; and Nature, in her simple progress, works the most infinitely diversified effects by the slighest modifications in the means she employs." Difference in the Digestive Powers of Animals. 199. Mr. Majendie fed a dog upon sugar and distilled water. In about a fortnight it became lean. On the 21st day an ulcer appeared in the centre of the |