176 
W. D. HALLIBURTON. 
portions of these were allowed to crystallise on a glass slide, 
and then examined with the microscope ; they were found to pre- 
sent the following appearances : — The crystals were single, and 
also in clusters and star-shaped masses. They varied in size 
considerably ; the average length was '07 to -08 mm., and the 
breadth varied from ‘01 to ‘001 mm. 
At first sight the star-shaped clusters reminded one of leucin 
or tyrosin, but closer investigation showed that they were not 
composed of these materials. They had a slightly brownish 
tinge, and the crystals were oblique rhombic columns. Some 
of these were so thin that they lay flat on the slide as rhombic 
plates ; the angles of these rhombs were measured by means of 
a goniometer stage attached to the microscope. The acute 
angle was found to be very acute, being on the average 39° 25', 
the obtuse angle being therefore 140° 35'. 
They did not polarise light. 
They were readily soluble in water, soluble with difficulty in 
alcohol. From the alcoholic solution they could be recrystallised. 
The crystals so obtained were slenderer, and had lost their 
brownish tint. 
2. The other part was dissolved by adding hydric sulphate. 
This solution was diluted and boiled for half an hour; it was 
then found to have the power of reducing copper salts. 
We have now data amply sufficient for the identification of 
this body. It is, in fact, chitin. 
It will be here convenient to enumerate the properties of 
chitin as at present known, and afterwards to point out the 
resemblances between it and the body obtained from the cartilage 
of Sepia. 
The Properties of Chitin are as follows: — It is a white 
amorphous body, insoluble in water, in weak acids, and in 
boiling concentrated alkalies ; soluble in strong acids. When 
dissolved in sulphuric acid it yields a body which reduces 
copper salts. This was supposed by Berthelot to be a ferment- 
able sugar, 1 but the researches of Ledderhose 2 have shown 
1 Berthelot, ‘ Comptes Rendues,’ xlvii, 227. 
2 Ledderhose, “ Ueber Chitin, und seine Spaltungsproaukte,” ‘ Zeitschrift 
