178 
W. D. HALLIBURTON. 
slide, the following were the results obtained : they were 
colourless , 1 and their form was that of flat rhombic columns 
radiating from various centres ; measurement of the acute 
angles of some of the more perfect of these gave as an average 
39 ° 25 '. 
The crystals had no action on polarized light. 
Having thus seen the properties of the substance obtained 
from the cartilage of Sepia, and that generally known as chitin 
occurring in the exoskeleton of insects, Crustacea, and other 
invertebrates, we can proceed to compare them; and can do so 
most readily by means of the following table : 
Substance prepared from 
Cartilage of Sepia. 
Substance prepared from 
Chitin. 
Condition. 
Action of water . . . 
Action of weak acids . 
Action of boiling alkalies 
Action of hydrochloric 
acid (in the cold) 
Action of sulphuric acid 
Prolonged action of hot 
hydrochloric acid 
Amorphous, white. 
Insoluble. 
Insoluble. 
Insoluble. 
Soluble : reprecipitated 
by adding water. 
Soluble : the solution 
reducing cupric salts 
The solution becomes 
brown, and a crystal- 
line substance can be 
obtained from it. 
Amorphous, white. 
Insoluble. 
Insoluble. 
Insoluble. 
Soluble : reprecipitated 
by adding water. 
Soluble : the solution 
reducing cupric salts 
The solution becomes 
brown, and a crystal- 
line substance (hydro- 
chlorate of glycosa- 
mine) can be obtained 
from it. 
That the crystalline substance obtained from the cartilage of 
Sepia is really hydrochlorate of glycosamine is seen by study- 
ing its properties, under the following heads : 
Its crystalline form ; including the measurement of its 
angles ; the very acute angle is quite characteristic. 
1 In more impure crystals sent by Professor Gamgee, the same light-brown 
tinge was noticed, as in those prepared by me from cockroaches. 
