NOTE I., CHAPTER I., p. 17. THE CHEMICAL COMPOSITION OF THE EXOSKELETON.
Reading edition
NOTE I., CHAPTER I., p. 17. THE CHEMICAL COMPOSITION OF THE EXOSKELETON.
The harder parts of the exoskeleton of the crayfish contain rather more than half their weight of calcareous salts. Of these nearly seven-eighths consist of carbonate of lime, the rest being phosphate of lime.
The animal matter consists for the most part of a peculiar substance termed Chitin, which enters into the composition of the hard parts not only of the Arthropoda in general but of many other invertebrated animals. Chitin is not dissolved even by hot caustic alkalies, whence the use of solutions of caustic potash and soda in cleaning the skeletons of crayfishes. It is soluble in cold concentrated hydrochloric acid without change, and may be precipitated from its solution by the addition of water.
Chitin contains nitrogen, and according to the latest investigations (Ledderhose, “Ueber Chitin und seine Spaltungs-produkte:” Zeitschrift für Physiologische Chemie, II. 1879) its composition is represented by the formula C15H26N2O10 .