274 
iSMFi’H. 
Whatever the exact chemical relation between the two pig- 
ments may be, and whether or no the one can be converted 
into the other in the organism, it is clear that the red 
tetronerythrin is a distinct body from the yellow lutein, and 
that where the two occur together in an admixture they caTi 
be separated by appropriate chemical means. Miss Newbigin 
lias shown that if excess of sodium chloride is added to an 
extract ot salmon muscle made by boiling the muscle with 
alcohol and caustic soda, a red precipitate is thrown down, 
while the yellow pigment remains in solution. The red 
precipitate dissolves in ether to form a yellow fluid, but in 
absolute alcohol it forms a red fluid. In the di-y state it 
gives a blue colour with nitric or sulphuric acid, and this is 
considered the typical lipochrome reaction. 
The yellow pigment contained in the caustic filtrate differs 
from the red in several particulars. It does not give the blue 
lipochrome reaction wdth nitric or sulphuric acid, so that its 
inclusion in the category of lipochromes is not strictly 
correct, though its frequent occurrence with lipochrome and 
its similar solubility in ether and alcohol have led to its being 
commonly called a lipochrome pigment. Miss Xewbigin 
remarks, in relation to the yellow' pigment : ‘Mn the salmon 
the pigment occurs in the muscle, the ovary, and in large 
amount in the liver. It is ahvays in close association with 
fat, and its solubility seems to depend upon that of the 
associated fat. It does not apparently form compounds with 
the alkalies or alkaline earths,” like the red pigment. 
By applying these methods for the separation and detection 
of the two pigments in the crab, it is possible to make out the 
following points : 
If the shell of a Carcinus is boiled with 60 per cent, caustic 
potash to whicli some alcohol is added, a reddish-yellow' 
extract is obtained, and on adding excess of sodium chloride 
to this, a, pink precipitate is Jormed wdiich gives all the 
characteristic lipochrome reactions. The filtrate, how'evei-, is 
quite colourless, and does not show the presence of any yellow' 
pigment. 
