Previous to the seventeenth century, milk was considered as composed of casein, butterfat, and serum.Fabritius Bartolettus, philosopher and physician of Mantua, wrote in 1619 (1), "In lacte sunt tres partes,-butyrum, serum, caseus." But in a later book (2), which he probably wrote in 1628, he mentioned a "manna seri" which he obtained by evaporation of milk serum. He spoke of it as "sal seri essentiale, seunitrum," and described briefly its preparation and purification.Ettmiiller was the next of whom there is record to write of lactose. He described (3) in 1688 the evaporation of the whey and the purification of the crude lactose by recrystallization.In Venice in 1694 Ludovico Testi (4) advertised lactose as an invention of his own under the name of "saccharum lactis" and advocated it enthusiastically as a remedy for gout and other diseases. The identity of the "saccharum lactis" of Testi with the "manna seri" of Bartolletus was pointed out by Fick (5) a few years later.In India, lactose had been prepared previous to 1712, since Kaempfer (6) wrote of the "Brahmenes, qui etiam ex omnibus dulcibus, quin ex ipso lacte, saccharum eliciunt."It was recommended by Stussius (7) in 1713 as an antiscorbutic, diuretic, and febrifuge, and its medicinal use was further discussed by Trostius (8) in 1739. It is interesting to note that most of the affections for which Dyvernois (9) recommended lactose are traceable to improper intestinal elimination and the accompanying autointoxication.He mentioned melancholy, 85