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Chemical Nature of the Gelatinous Substance of Cassiopea

cent, protein, nitrogen and medusas

CHEMICAL NATURE OF THE GELATINOUS SUBSTANCE OF CASSIOPEA.

The chemical nature of the jelly-like substance (reserve substance) of various forms of medusa has been examined by several investigators, but so far as I am aware nothing has been definitely established as to the chemical nature of this puzzling structure.

Krukenberg (1882) considers this substance to be composed of protein material which is easily digested with either pepsin or trypsin and splits off leucin, tyrosin, and other substances not identified. Very recently Macallum (1903) published his extensive investigations on the inorganic constituents of the medusas Aurelia and Cyanea, and mentions in the text that "the jelly is constituted of an almost infinitesimally minute network formed of a proteid." In another place Macallum states that "it must be noted that the total amount of proteid in Aurelia is very small, ranging between one-seventh and one-eighth of 1 per cent of the total weight of the organism," but in no place in the paper does Macallum mention either the kind of protein present or give any analytical data to show how he determined the quantity of this protein. There are also some chemical observations of a qualitative nature made by Schulze in 1856 and by Schlossberger in 1856. Vernon (1895), who made extensive observations on the phenomena of respiratory exchange in various marine invertebrates, thinks that "the solid organic constituents may not consist by any means of pure proteid."

From the above we see that the true nature of the jelly or ground substance of the medusas is not determined; this makes it difficult to interpret the various changes noted in the present experiments. It is at once evident, however, that the solids can not be constituted as a whole by the ordinary protein, since the latter usually yields nitrogen to the extent of 12 to 18 per cent, contrasted with 3 per cent in the dried Cassiopea.

Even if we calculate the nitrogen in ash-free solids, the value rises no higher than 6 per cent; but this nitrogen value (about 6 per cent) is interesting in view of the fact that it is the value found by Schloss berger (1856) for the chitinous substance. Although the nitrogen content in the solids alone is not adequate to show that we are dealing with a chitin-like substance, yet recent investigations by Henze (1908) on the identity of the framework of siphonophone with chitin and, further, the wide occurrence of chitin in numerous marine inver tebrates as shown by Irwin (see Armstrong, 1912) indicate that the ground-substance of the medusas might be similar. If this supposi tion turns out to be true, its biological significance becomes at once evident, since chitin is closely related to mucin, which in turn is closely related to the cartilage of the vertebrate skeleton.