In our previous papers we have shown that the black pigment found in the mammary tissue of sows of various coloured breeds is related to the colour rather than to the sexual condition of the pig. We have also pointed out that this conclusion is contrary to the statements of bacon curers who rely on the presence of this pigment for an indication as to whether or not a sow is ‘on heat.’ Their method of testing the condition of the sow has been described by us in a former paper. It follows from the assumption made by the bacon curers that pigment should not be present in the ‘belly pieces’ of spayed sows (or to be strictly accurate, of sows spayed in early life, before the mammary ducts and glands have undergone development).