Chinese Journal of Physiology

THYROID AND HAIR GROWTH 65

As we have already mentioned, thyroid feeding does not entirely compensate for lack of sufficient nutrition.

Examples of individual experiments are given in table 2.

Iodine. The dosage of iodine ranged from 0.2-1.2 gm. In more than half of the cases no change was produced, while the remainder exhibited acceleration and retardation of hair growth in about equal proportions. The results are compared with the individual hair growth rates during partial feeding, as the iodine experiments and those following were carried out under this condition, the object being to see if any of the substances investigated could replace thyroid.

Experiments Total Acceleration Nochange Retardation dosage gm S.P. M.N. S.P. U.N. S§.P. MN.

IV. Partial 0.2-1.3 87 (7) 11 (2) 58 (11) 47(9) 5 (1) 42 (8) feeding +thyroid

IX. Partial 0.2-1.2 23 (4) 6 (1) 65 (11) 41 (7) 12 (2) 53 (9) feeding +jodine

X. Partial 0.1-0.2 20(8) 7 (1) 55 (8) 33 (5) 27 (4) 60(9) feeding + tyrosine

XI. Partial 0.1-0.3 36(4) 0 18 (2) 18 (2) 46 (5) §2 (9) feeding

+ tryptophane

S.P., comparison with partial feeding rate (simultaneous control). M,N., comparison with mean normal rate,

Tyrosine. In 18 observations, there were four accelerations, 6 tetardations and 8 without change. Two control observations made with the acid solvent (N/100 HCl) alone resulted in a slight acceleration of

hair growth. In spite of this, there were more cases of retardation than acceleration.

Tryptophane. The largest number of retardations were recorded following tryptophane feeding.

While none of these three substances can equal the thyroid in their influence on hair growth, it is interesting to note that the effect of iodine approaches that of thyroid most closely and that tyrosine retards less than tryptophane. We would not lay undue stress on these observations except in so far that they show that thyroid cannot be replaced by any one of its constituents with the range of dosage given.