130 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 
appear to be rendered sterile for the tins are heated in steam 
under pressure to a temperature well over 100°C. The sealed 
tins may be incubated at 37° C. for weeks without “ blowing,” 
or giving any indications of growth of micro-organisms when 
they are opened. Of course, the possibility is not entirely 
excluded of certain spores remaining alive in the oily parts 
of the fish or medium even under the conditions of the sterilisa- 
tion. Also some tins are septic and become blown on keeping, 
but this does not appear to occur when the factory management 
is all that it ought to be. 
One may, therefore, exclude bacterial action as a cause of 
ripening, or if it does occur the precise nature and conditions 
must be very different from those usually associated with 
anaerobic putrefactive processes. Now, the changes that occur 
in the process of maturation do seem to suggest an autolytic 
process, though there is the difficulty of supposing intra-cellular 
enzymes to remain active after having been submitted to 
temperatures that are sufficient to produce sterility with 
regard to bacterial micro-organisms and ordinary moulds. 
Assuming, however, that there are enzymes in the flesh or 
media that are not destroyed by the processing, the changes 
that occur as the results of ripening seem, at first sight, to be 
such as would fit this hypothesis—supposing that these enzymes 
are present in very small quantities and that they do not 
increase, for the assumed autolytic changes go on extremely 
slowly in the usual conditions. 
If this is so, if the ripening is a process of autolysis He 
to specific, intra-cellular enzymes normally present in the 
flesh of the fish, and not entirely destroyed by the sterilisation, 
then we ought to expect that the change that occurs is a 
proteolytic one, the proteids of the flesh being partially split 
up with the appearance of amino-acids. The flavour of the 
matured product would then be due to the traces of certain 
amino-acids produced as the results of proteolysis. This is 
what occurs in the process of ripening of salted herrings. The 
