180 
W. D. HALLIBURTON. 
2. By boiling it with sulphuric acid a body which reduces 
cupric salts is formed. 
3. By boiling it with hydrochloric acid, crystals of hydro- 
chlorate of glycosamine are obtained. 
The percentage of chitin present (the average of three 
analyses) is T01. 
It should be here mentioned that I performed some control 
experiments with the cartilage of two vertebrate animals, viz. 
the cat and rabbit, taking the rib cartilages in each instance ; 
but in neither was there any residue after boiling with con- 
centrated caustic potash. 
The cartilage, then, of the two invertebrate animals I have 
examined differs in a very important way from that of verte- 
brates ; namely, in containing chitin in its composition. 
C. — The Existence of Chitin in the Liver of 
. Limulus. 
The following analysis is merely a qualitative one, and shows 
conclusively, that chitin is present in the liver of Limulus, 
though whether actually in the liver-cells, or in the connective 
tissue of that organ, which is very abundant, I am unable to 
say. It seems more probable that the latter is the correct 
view. 
The livers of four king-crabs, which had just been killed, 
were digested with a large amount of caustic potash for three 
or four days. After this time most of the constituents of the 
liver were dissolved, hut there was a considerable amount of 
insoluble residue. This was filtered off. The filtrate was 
brown, and perfectly clear ; the residue was also of a brown 
colour, thick, muddy, and partially flocculent. The residue 
was collected, washed with water, and again digested with 
potash of the same strength; it was thus obtained of a lighter 
colour; by repeating the process, almost colourless flocculi 
were obtained. It (the residue) was then washed w'ith distilled 
water and found to be insoluble in boiling water, and also in 
concentrated boiling potash. It was soluble in concentrated 
