TRANSCUTANEOUS ABSORPTION OF VITAMIN A , 173 in the slope of the curve during the last week is due largely to the loss in body weight, which was coincident with an attack of sniffles in one rat. At the beginning of the test period, the average body weight of the control group was 50 gm. and that of the test group 46 gm. At the end of the experimental period of eight weeks, rats in the control group exhibited an average gain in weight of 49 gm. whereas, during the same period, their litter mates in the test group showed an average in- crease of 89 gin. 50 m 20 I GROUP / / • 4o -- • 3o o o io N o --10 I 2 3 4 WEEKS OF TEST PERIODS Chart II.--Comparative average gains in weight of vitamin A-deficient rats receiv- ing daily topical applications of equivalent amounts of petrolatum containing varying concentrations of vitamin A. Chart II presents a summary of results of a series of curative experi- ments. For all of the curative experi- ments, a total of 45 rats, pooled from six litters, were divided into test groups at a time when growth curves indicated that their bodily stores of vitamin A had been depleted by the feeding, from weaning age, of the vitamin A-free diet. Fourteen rats were continued on the diet without supplements of vitamin A until death or until they were sacrificed in a moribund state. These animals served as the negative controls which are included in the group designated as "V" in the chart. Four groups, whose average gains in weight are depicted by the graphs in Chart II, received daily, through- out test periods of either four or five weeks, topical applications to their skins of equivalent amounts of petrolatum containing varying con- centrations of vitamin A, as shown in the following tabulation. Groups Concen- Av. Body trations of Wt. at Vitamin A in No. of Beginning Petrolatum Rats of Test Applied to in Period, Skins, I.U. Group Gm. per Gm. I 3 124 2100 II 4 117 600 III 6 108 450 IV 4 119 100 V 14 120 0 Since all of the rats in the test groups were under observation for four weeks, but some were not con- tinued through the fifth week, the graphs in the chart have been limited to the first four weeks of the test period. The average curve for group V is representative of only 11 negative control rats which survived during the first three weeks of the test

17zt JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS period. All of these animals lost weight during the second and third weeks, but four survived through the fourth w6ek. In contrast with the negative controls, all of the four groups of rats, which received topical appli- cations'of peirolatum containing vitamin A, exhibited average gains in weight during the test period. Average results of this series of experiments point to some correlation between the concentration of vita- min A in the petrolatum base, which was applied to skins, and the growth responses of the vitamin A-deficient rats. It is evident, however, that this correlation is not quantitative. In fact, ii is a matter of common knowledge that bioassays fail to yield quantitative relationships be- tween dosages of vitamin A adminis- tered orally and growth responses of vitamin-deficient rats. In all of the experiments on groups I to IV, inclusive, which have been summarized in Chart II, the source of vitamin A was maintained in static contact with rats' skins •or two hours. A subsequent series of experiments wa• undertaken with the objective of determining the influence of massage upon the rate of transcutaneous absorption of vita- min A. Results of this series of experi- ments are summarized in Chart III. Equivalent amounts of petrolatum, containing 450 units of vitamin A per gram, were applied daily and maintained in contact with skins of all rats for periods of two hours. In tests on one group of six rats (Group III of Chart II), this contact was entirely static. However in experi- ments on the other group of foul animals, the petrolatum containing the vitamin concentrate was rubbed gently with an index finger over the test area of skin at intervals during the period of contact with skin. The total time of rubbing was thirty minutes. At the beginning of the test periods, both groups of rats showed approxi•nately equivalent average body weights, viz., 108 and 106 gm. ' 60 V! • 5o -- • •o • •o o i 2 3 4 5 WEEKS OF TEST PERIODS Chart III.--Comparative average gains in weight of rats receiving topical applications, with or without massage, of equivalent amounts of petrolatum containing a,50 units of vitamin A per gram. O, applications without massage to 6 rats O, applications with massage to a, rats. The curves of Chart III demon- skrate that, throughout the test periods, vitamin A-deficient rats receiving topical applications of vitamin A in the petrolatum with massage made better gains in weight than did the animals to whose skins comparable amounts of the vita-