244 Ornfiotininj in Soim 



subsequently liad two litters, each of eight pigs, which were suckled. 

 The first litter was born on March '29th, 1914, and the second on October 

 13th, 1914. On February 15th, 1915, the sow was killed, when all 

 the mammary glands (including those previously examined) were closely 

 searched for jjigment. None whatever could be found. 



(2) In a Large Black sow two glands were examined for pigment 

 in the same manner as that adopted in the first experiment. The first 

 gland on the right side did not appear to contain pigment, but in the 

 fifth gland on the other side some was found a little distance from the 

 nipple. The sow had a litter of nine on March 22nd and a litter of 

 eleven on October iSth, 1914, and lactated normally. AVhen the animal 

 was killed on February 15th, 1915, not a trace of pigment was found 

 in any of the glands whicli were carefully examined. 



(3) In a Berkshire sow the right anterior gland was found to contain 

 a large cpantity of pigment, but none was found in the fourth gland on 

 the left side. The sow on April 14th had a Utter of six pigs and on 

 October 13th a litter of five pigs which were suckled normally. On 

 killing the sow on February 15th, 1915, no mammary pigment could 

 be detected. 



(4) In a Large Black sow the first right and third left glands were 

 examined and each was seen to possess much pigment. The sow pro- 

 duced a litter of nine young on March 23rd, and a litter of eight on 

 October 15th. Both were suckled. On killing the animal on February 

 15th, 1915, a very slight trace of dark pigment was found just 

 below the first teat on the left side, but none in association with either 

 of the other teats, so it was evident that pigment had been removed 

 from the glands previously searched. 



Each of the sows at the time of kilHng had large protruding follicles 

 in the ovaries, indicating the approach of another heat period, and 

 there was every indication that the animals w-ere sexually normal. 



The above described experiments prove very clearly that the dark 

 pigment which so frequently occurs in the mammary tissue in pigs of 

 coloured breeds, and which we have shown to exist even in the embryo, 

 may be no longer present in sows which have been bred from. The 

 precise period (or periods) at which this pigment disappears is still 

 unknown, but there is a strong presumption that its removal takes place 

 either during the progress of lactation, or in the period of pregnancy 

 when the mammary glands are being built up preparatory to the secretion 

 of milk. The fact that mammary pigment can become diminished in 

 quantity to the point of disappearing altogether, is a point of great 



