This gas is frequently called air. The gas contained in the pneumatophore of Physalia was analysed by Schloessing and Richard, C. R. cxxii. 1896, p. 615, and found to consist of CO2, 1.7 parts, O 15.1, nitrogen and argon, 83.2.
The chemical composition of the substance here called "chitin" has not been accurately determined. An analysis of two specimens of Velella bladders gave 9.71 and 10.35 per cent of nitrogen, which is higher than that of chitin and nearer to that of mucin.
Zool. Jahrb. Suppl. 1904, p. 347.
Johns Hopkins Univ. Circ. x. 1891, p. 91.
C. Chun, Abh. Senck. Nat. Ges. Frankfort, xvi. 1891.