STRUCTURE AND GROWTH
dark side in the thickness of the walls distinguished. The delineation, at the same time, proves how important a share is taken by the intercellular substance in the formation of the firm structure of cartilage.
The cartilages of the foetus do not altogether accord in chemical constitution with those of the adult, since we can obtain from them by boiling but a small quantity of a gelatinous substance, and that only with great difficulty, and they afford no true gelatine (capable of forming a jelly). I boiled some unossified cartilages, consisting of apophyses of the femur and cartilaginous portions of the scapule, taken from several embryo pigs, measuring three and a half inches in length. After twelve hours’ boiling, they entirely crumbled into very small scales, which gave a variegated appearance to water in which they were stirred about, and appeared under the microscope extremely thin and granulous. ‘The fluid, when filtered and evaporated almost to dryness, did not coagulate. Alcohol produced a copious precipitate, which was dried, afterwards dissolved in boiling water, and then evaporated almost to dryness; still no coagulation took place. Alum, however, clouded the fluid, and acetic acid had the same effect, but in a much slighter degree. As the quantity of cartilage made use of in the foregoing experiment was too small, I made a further investigation with cartilage which had already become ossified, from the same embryos, namely, the frontal and parietal bones, scapule, humerus, femur, and some ribs. The unossified parts were removed as cleanly as possible from all the bones. The earthy matter was withdrawn by hydrochloric acid; the cartilages were then washed with water, and boiled for twenty-four hours. Under this process they fell to pieces very slowly, meanwhile numerous little glttering scales appeared in the fluid, which, after being dried, resembled very minute fish-scales, and exhibited a beautiful play of colours. They were,perhaps, the lamellae described by Deutsch, which surround the minute medullary canaliculi. The form of most of the pieces of cartilage remained perfectly recognizable, and was but slightly altered. They looked of a yellowish-white colour, and not at all gelatinous, as substances usually do when about to be transformed into gelatine. The fluid was filtered from these little scales and pieces of cartilage, and then evaporated almost
