120 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS and the effect of the secondary valence bonds which eventually will be re-established in the fiber plus the tendency to a'higher state of entropy, considerable strain is placed on the reformed disulfide bonds and it is therefore not sur- prising that in actual beauty shop practice the relaxation of a "perma- rierit" wave is riot uncommon. Certain commercial waving proc- esses have been designed to over- come this difficulty. In these proc- esses an absorbent pad is placed around each curl after the waving lotion (ammonium thioglycolate) has acted sufficiently long and be- fore the fixative (oxidizing) solution is applied. These pads withdraw the excess waving lotion from the spaces between the fibers. by cap- illary action. By removing the ex- cess thioglycolate from the outside of the fiber without removing sig- nificant amounts of solution from within the fiber, they tend to reverse the action of the reducing agent. A little reflection will readily show that at the end of the reducing step the ratio of dithiodiglycolate to thioglycolate is higher within the fiber than it is outside of the fiber. Going back to the equation showing the reaction of hair with thioglycol- ares given at the beginning of this paper, it can certainly be expected that the reaction will not go any further to the right, but since it is an equilibrium reaction and it so happens that the Redox potentials of cysteine/cystine and thioglycolic acid/dithioglycolic acid systems are the same (16), it may be reversed. Under the influence of the ad- sorbent pads we thus may have a partial reoxidation, which under optimum conditions may be suffi- cient to give some permanent set to the hair. The contribution of the absorbent pad to the success of the cold wave is more than inducing the reoxidation of sulfhydryl group. By withdrawing the waving lotion from the air spaces surrounding the hair fibers and rebuilding some di- sulfide linkages, the adsorbent pads initiate the deswelling of the hair fibers. Since this is a gradual and controllable process, it allows the amino acid side chains to reorient themselves in positions which are more favorable to the formation of desirable salt linkages and hydrogen bonds. But beyond this, the slow deswelling action af the absorbent pads permits the sulfhydryl groups which were spacially too far sepa- rated to be oxidized to disulfides to be brought into juxtaposition so that they can be thus oxidized. Briefly stated, the function of the absorbent pad is therefore the ini- tiation of the rebuilding of the co- valent --3--S-- bonds, the gradual deswelling of the hair fibers thus allowing the establishing of desir- able coordinate valence bonds, and the bringing together spacially '---SH groups, which would otherwise be resistant to oxidation to disulfides. In the discussion of the chemistry of the cold wave process the picture has been intentionally oversimpli- fied. In the treatment of various steps it has been assumed that the hair fiber possesses a homogeneous

PERMANENT WAVING OF HUMAN HAIR: THE COLD PROCESS 121 structure. This obviously is not true. As yet very little is known as to. what role the cuticle, the cortex, and the medulla play in the process of cold waving. Until such time as more data and new experimental tools become available, it seems ad- visable to use the oversimplified concept to further the understanding of the cold wave process. The re- cent publications by Phillips (8), Stoves (11, 17), Lehmann (18), Mercer and Rees (19), Hock and McMurdie (20), and others indicate that the problem of the structure of -keratin fibers as related to their chemical reactivity is receiving more and more attention. Current widespread interest in the toxicological properties of thiogly- colares has revealed the fact that very few experimental data on this subject have been published. It is obvious that neither eloquent editor- ials nor vociferous accusations or denials will lead to the solution of the problem. In private correspondence from clinicians, several of these have stated that they have patients which show "typical" symptoms of thioglycolate poisoning. It is strange that these "typical" symp- toms which one clinician describes, often 3iffer radically from those de- scribed by another clinician. As yet ho authoritative work has been published on the mode of action of thioglycolate on the living organism and on the symtomatology of thio- glycolate poisoning. In this labora- tory, using rabbits as test animals, it was found that it is possible to kill the animals if sufficiently large doses of ammonium thioglycolate are applied percutaneously over a long enough time. When the organs and tissues of animals which had thus succumbed were examined macroscopically and microscopically by a competent pathologist, no pro- nounced changes from the normal controls could be observed. Work now in progress suggests the at- tractive hypothesis that the action of thioglycolates may be to deprive the body of labile methyl groups (from methionine and choline), these being used to detoxify the thiogly- colate. In this connection, it is interesting to note that thiodigly- colic acid, given either percutane- ousl? or orally by stomach tube, seems to be quite well tolerated by experimental animals. Percutaneous.applications of mod- erate amounts of thioglycolates are readily tolerated by experimental animals. Using the Draize tech- nique (21) it was found that the daily application of a commercial cold wave lotion for twenty days in amounts equivalent to 100 mi. per 50 kg. of body weight produced no apparent ill effects on rabbits as evidenced by the growth curve, red and white cell counts, as well as ex- amination of the organs at necropsy. While it is not justifiable to trans- late these findings directly to the human being without further work, they do seem to indicate that the factor of safety is quite large, since only a very small fraction of 100 mi. can possibly be abs6rbed by the patron during a cold wave.