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OF CARTILAGE.

to dryness. It did not exhibit any trace of coagulation after standing twenty-four hours. After being dried, it was again dissolved in boiling water, on which occasion, however, a por- tion remained undissolved. It was, therefore, filtered; the fluid was copiously precipitated by alum, and the precipitate was, for the most part, although not entirely, dissolved, on the addition of alum in excess. Acetic acid likewise rendered the fluid very turbid, and an excess of acid did not entirely remove the cloudiness. It was copiously precipitated by tincture of gall-nuts, and acetic acid removed this precipitate again, leaving a very slight turbidness. (Acetic acid likewise completely dis- solves the precipitate obtained from glue by tincture of gall- nuts, therefore glue, when dissolved in acetic acid, will not be precipitated by the tincture.) According to these reactions, the gelatinous substance obtained appears to be chondrin, not- withstanding that it was obtained from ossified cartilage. The question, therefore, arises—does the cartilaginous substance which is connected with earthy matter in the foetus really yield chondrin instead of the gelatine of bone, or was there much unossified cartilage still contained in what appeared to be ossified, and was that the sole source of the chondrin? The point is, at all events, worthy of renewed investigation. It is surprising that the foetal cartilages should exhibit so great a resistance to the action of boiling water, and that although they yield a small quantity of a gelatinous substance, they do not afford any which has the property of gelatinizing.

The formative processes of cartilage hitherto described, proceed, as it appears, without the presence of vessels in the structure ; such at least is the case in thin cartilages, to which probably the fluid parts of the blood can penetrate from the vessels of the neighbouring tissues. In the branchial rays of the fish, for example, I could not find any space in which ves- sels could have existed; throughout the structure masses of cartilage and cartilage-corpuscles were to be seen, but no canals which could have been traversed by vessels.

The manner in which ossification proceeds now becomes an interesting object of inquiry. The investigation is best pursued by making very fine sections with a razor, from the half-ossified cartilages of the extremities, vertebrae, or coccyx, of the larva of Pelobates fuscus. The little cartilage-cells, which