CHITIN IN THE CARTILAGES OF LIMULUS AND SEPIA. 175 
3. Mucin is present, as is shown by acetic acid causing a 
precipitate when added to the solution in Baryta water. 
4. Gelatin, if present at all, is present in very minute 
quantity, as is shown by tannin producing a precipitate in the 
watery solution; but not present in quantity sufficient to cause 
gelatinisation. 
5. The basis of the cartilage is a substance soluble in 
alkalies. Chondrin is now regarded 1 by many as merely a 
mixture of mucin and gelatin ; it would seem that this is what 
we have here ; the tests for both these bodies can be obtained ; 
that the gelatinous element is, however, present to a slight 
extent only is shown by the fact that gelatinisation does not 
take place ; or this latter fact may be due to the coexistence of 
chitin mixed with it. 
6. That in addition to this chondrin-like body, the cartilage 
contains a body insoluble even in boiling alkalies. This 
residue after boiling with potash will presently be shown to 
consist of chitin. 
7. Little can be concluded from the fact that a sugar-like 
body reducing copper salts can be obtained by boiling with 
dilute sulphuric acid, since chondrin, mucin, and chitin all 
behave in this way. 
We have next to consider the composition of the residue left 
after boiling with solution of potash. 
A large quantity of the cartilage was taken, potash added ; 
the residue, a colourless amorphous body, collected, and washed 
thoroughly by decantation with distilled water. It was divided 
into two parts, which were treated in the following way : 
1. One part was dissolved by adding hydrochloric acid to it; 
a clear solution was formed. This solution gave the following 
tests : 
a. On adding water it was reprecipitated. 
b. Another portion was treated in a water-bath for about an 
hour. The colour of the solution became brown. On evapo- 
rating to dryness crystals of a brownish hue were formed ; 
1 Mowckowitz, “Zur Histochemie des Bindegewebes,” * Verkandl. d. Na- 
lurkist. Med. Vereins zu Heidelberg,’ Vol. i, Part 5. 
