INDIANA UNIVERSITY BLOOMINGTON, INDIANA DEPARTMENT OF ZOOLOGY Feb, 19, 1962 20h Jordan Hall Dr. Joshua Lederberg Dept. of Genetics Stanford University Palo Alto, Calif. Dear Josh: it was kind of you to ask Dr, Richard S. Young, fol- lowing my letter of Dec. 15 to you, to send me a statement con- cerning available information about the experiments on weight- lessness simulation. As you will see from the enclosed duplications, T followed up his letter of Jan.17 by requesting certain specific reorints, two from him, and one from Drs. Stone and Letko. Although it is now nearly four weeks since I sent these two letters, I have had no reoly whatever. This situa- tion illustrates my previous experiences in trying to find out what if anything had been done along the lines I suggested in Science some years aso. I wonder whether from your vontage point you could find out what the hitch is and/or, better, whether ard how I could obtain some information about the follow-up, if any, to my suggestions. AFL A “With all best wishes, Yours sincerely. HIM:slh H. J. “rller enc. duplication of corre- snondence with Pr. Young, etc. Dem Jot - A vvonpine Dick 2 har thHl upeting for a pull sr bes Imgrinice brs be tom dirall Mim roe Fo gee Bias pn iff Ae pet Auth raul mt f bop emule , Thruyls ASTIN Aenittones unteo. VASA Heo gttans to purr Lihue coforimto Ail ote cht wee ty won, Tuck Ada Dw., Way. 25- 0.6. Bist AM aman parrot pM heme oJ tone lng ay 9g tiny rbliing rept mdr Ap a civiliaae hymstior s Reprinted from Scuunce, October 3, 1958, Vol. 128, No, 3327, page 772. Approximation to a Gravity-Free Situation for the Human Organism Achievable at Moderate Expense So far as their effects on the human organism are concerned, the chief pecu- liarities of weightlessness consist in (i) the cessation of unidirectional stimula- tion of the vestibular system, together with the sequelae accruing therefrom through reactions of the autonomic and central nervous systems, and (ii) the let- ting up of the hydrostatic drag on the circulatory system, especially that asso- ciated with the erect posture of man. Both of these peculiarities can be ap- proximated to a considerable degree by a combination of relatively simple de- vices, The use of these would enable data on the effects of this pseudo-weight- lessness, maintained for several hours at least, to be obtained long before the still exceedingly costly direct tests of subject- ing human beings to prolonged free fall can be carried out by Western sci- entists. By far the greater portion of the hy- drostatic drag is absent in human beings whose body axis is in a horizontal posi- tion, as it is when they are recumbent. Most of the remainder can be evened out and in effect nullified by subjecting them to a moderate spinning motion about their horizontal axis, through the auto- matic rotation of a cylinder within which they are held. At the same time, little sense of the pressure caused by their body weight would remain if the body, including the limbs, were encased in a skin-tight envelope, and held immersed in a brine having the same specific grav- itv as the average for the body itself. Considerable freedom of movement can be allowed for the limbs. The head can be encased in a transparent helmet that is serviced for respiration and oral communication. It is to be held with its axis in alignment with the body axis, That is, the head is not permitted tilting movements that would set its axis at an angle to that of the body; however, it is left free to carry out any desired volun- tary movements of rotation on its axis. A field of view, imitative of furnishings and, for example, of a window showing a skyscape, would be arranged that re- mained in a fixed position with reference to the subject. Thus the field of view would spin together with the subject himself, and the subject would lack the visual stimuli associated with an imposed rotary movement. The subject, after having been fast- ened within the cylinder, would at first be at rest but by insensible degrees would be subjected to a rotary movement about his horizontal axis, at a speed that in- creased until it attained the psycho- physiological optimum for disengaging his vestibular apparatus from an effec- tive pull by gravity in any given direc- tion. Thereafter the motion is to be kept smooth and steady. Preliminary experi- ments have shown that under such cir- cumstances, so long as the subject’s head remains with its original relation to the body axis, he soon becomes quite un- aware of the rotary movement as such. This is because the fluid in his semicir- cular canals has come to rest, in relation to their walls (except for any voluntary axial turning movements, which then give rise only to the effects usual for them), and because he has no notifica- tion of the imposed rotation through vision and very little through skin or in- ternal bodily pressures. It is likely that a suitable speed of rotation could be found which was too fast, in relation to the sensitivity of that part of the vestibular apparatus which detects translational (linear) accelera- tion or gravity in any one direction, to allow such stimuli to accumulate to an appreciable degree. That is, not so rapid a periodicity should be required to transcend “flicker” in the case of the sensation of linear acceleration here in question as in the case of optical flashes. For psychological and physiological pur- poses, a condition approximating that of weightlessness or free fall would thereby have been achieved. Essentially the same mechanism has long been used for nulli- fying gravity in studies on plants, but the speed of rotation for this apparatus, called a clinostat, can be much slower because of the much slower reactivity of plant tissues. Among other questions that would thereby be opened for investigation are those concerned with the effects, on free- fall tolerance, of individual differences (as between persons of differing tend- encies to become giddy or motion-sick) and of the effects of differing physiolog- ical conditions and of diverse drugs (such as those used against motion sick- ness). The relatively small cost of the apparatus required for such experiments, and the relatively short time required for its construction, recommend it for pilot studies on the effects of fairly prolonged weightlessness (1). H. J. Mutrer Depariment of Zoology, Indiana University, Bloomington Note 1. This report is based upon a paper read at Sym- posium on Possible Uses of Earth Satellites for Life-Sciences Experiments, Washington, D.C., 17 May 1958; Contribution No. 659 of Zoology Department, Indiana University. 21 May 1958