Why is fish oil (of the sprat, pilchard, etc.) very lia-able to become foetid?
Because, in general, the oil is obtained from the livers of the fish, in which it is lodged in cells; but, as it cannot be procured completely from livers by mere boiling, they are allowed to become a little putrid, that the oil may be more readily extracted, by the rupturing of the cells. Along with the oil various other impurities are obtained, as bile, gelatinous matter, etc.
