In the present paper lactose content of 392 milk samples from 200 mothers were examined and the following 10 questions were studied.
1. As to the human milk lactose content according to the inten-sity of Arakawa's reaction, human milk positive to Arakawa's reaction (7.64g/dl Cf. Table 5) is generally higher in lactose content than the Arakawa-negative milk (6.97g/dl). And lactose content of Arakawa-negative milk fluctuates in a wider range than that of Ara-kawa-positive milk.
2. Monthly variation of lactose content shows that it is slightly lower in cold seasons than in other seasons both in Arakawa-positive and -negative milks. But the seasonal difference itself is not so large as the difference between Arakawa-positive and -negative milks.
3. As to the lactose content of human milk according to Ara-kawa's reaction and according to the period of lactation (Cf. Tables 7 and 8), it is generally the highest in the middle mature period, but in Arakawa-positive milk alone lactose content keeps almost constant in every period of lactation, (colostrum is excepted, of course). Colo-strum milk (0-14 days after delivery) was excluded from this experi-ment, for, according to Pfeiffer, ¹¹⁾ Adriance¹⁴⁾ and Lowenfeld³⁹⁾ the lactose content rises rapidly during the first few days or during the first two weeks, and then returns to the normal level.
4. Concerning the variation of lactose content of Arakawa-posi- tive and -negative milks according to the age of mothers (Cf. Table 9), there is no relation depending on the age. Of course, such a strik-ing difference as between Arakawa-positive and -negative cases is not seen among mothers of different ages.
5. As to the lactose content of human milk according to.Ara-kawa's reaction and to different sides of breast (Cf. Table 10), it is almost the same amount on either side, both in Arakawa-positive and -negative milks. That is to say, Arakawa-positive mothers secrete lactose-rich milk on both sides and Arakawa-negative mothers secrete lactose-poor milk.
6. If all the milk samples are distributed according to the in-tensity of Arakawa's reaction and according to the amount of lac-tose, , and if a dissecting line is drawn between 7.3g/dl and 7.2g/dl, 80% of Arakawa-positive milk ranks above the line, while 60% of A-rakawa-negative milk ranks below the line.
7. As to the human milk lactose according to the quantity of secretion and to Arakawa's reaction, 88% of Arakawa-positive milk secrete abundantly, and in the Arakawa-negative cases, the weaker the reaction, the smaller is the percentage of the cases with abundant secretion.
8. Concerning the difference of lactose content between both sides of the breast according to Arakawa's reaction (Cf. Table 14) the difference is twice as large a one in the Arakawa-negative case compared with the positive case.
9. In the cases of one and the same mothers with very different reaction on either side of the breast, there is almost no difference between the lactose content of positive and negative sides, and the lactose content in such cases corresponds to that of milk of the inter-mediate Arakawa reaction.
10. In the case of nutritional disturbances or under-grown ba-bies, such as atrophy or lues congenita, the lactose content is lower than that in other cases.
As summarized in different items above mentioned, lactose con-tent in human milk is generally different according to a number of different factors, but such a remarkable difference as between Araka-wa-positive and Arakawa-negative milks is never seen.