118 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 
seed, whatever it may be—either contams no proteid matter, 
or contains such as an insignificant trace resulting from the 
methods of preparation, but the oil on the fish tissue does contain 
nitrogen in some form, and this nitrogenous oil does not easily 
diffuse out from the tissue into the medium in the tin. In 
hermetics that are long matured there may be some diffusion 
out from the fish—thus, the highest results in the cases of the 
four samples examined were those of the French pilchards 
and the herrings in tomato sauce, both matured for about 
4 to 5 years. In the latter case the medium in the tin was a 
mixture of watery sauce and oil that had been squeezed out 
from the flesh of the fish. 
When pilchards, herrmgs and sprats are packed in oil in 
tins the oil is always watery. As a rule, the mixture is apparent, 
and the oil and water segregate at once, but in some cases 
(notably that of the Rodel sardines) the mixture was such as 
to pass through a dry Swedish filter paper as a pellucid liquid. 
After some weeks this separated into a thin layer of turbid 
watery solution and a layer of clear oil. The water thus incor- 
porated in the oil may amount to 4 to 7% of the weight of the 
mixture. 
The percentage of nitrogen in the dry, fat- 
free, ash-free residues. 
Obviously, the use of the term “ proteid” in these analyses 
is to be regarded as rather a convention than as indicative of 
some definite chemical substance: it 1s, however, employed 
as useful from the dietetic point of view, and may be regarded 
as some substance, or mixture of substances, contamimg from 
14:3 to 17-4°% of nitrogen. In considering the composition — 
of fresh and preserved fish from the pomt of view of methods 
of conservation it is better to speak of the percentage of nitrogen 
present rather than that of “ proteid,”’ assuming this to be 
nitrogen x 6-25 where the factor, 6-25, is an arbitrary one, 
