to the peripheral vestibular organ, and that there appear to be two groups with different conduction velocities. Moreover, a parallel light- and electronmicroscopic study has confirmed the existence of the direct cerebello-vestibular pathwayin the bullfrog by showing that section of the eighth nerve extracranially produces degeneration of both climbing and mossy fibers, as weil as characteristic retrograde changes in pathway in the frog implies that, at least in this form, the cerebellum is not involved in motor control exclusive- ly, but has a sensory regulatory role as well, Ropo_ro Linas WOLFGANG PRECHT STEPHEN T. KITAI American Medical Association, Institute for Biomedical Research, Chicago, Illinois 60610 the somas of Purkinje cells (15). The latter finding (Fig. 2, top) directly confirms the thesis that Purkinje cells send axons or axon collaterals to the vestibular organ. In addition, if the cerebellar cortex is removed, care being taken not to injure the cerebellar nuclei, one can demonstrate degenerating synaptic boutons in contact with the peripheral vestibular receptor cells (Fig. 2, bottom) (J75). The aforementioned results demonStrate the existence of a cerebellovestibular efferent system in the frog. Previous anatomical and physiological Studies have indicated the presence of an efferent system to the peripheral vestibular organ. In the case of the cat, light- (16) and electron-microscopical studies (27) have revealed efferent terminals on the vestibular receptor cells. Furthermore, direct-current potential changes have been recorded from the surface of the semicircular canals following stimulation of the central ner- vous system (/8). In the frog, recent electron-microscopical studies have verified the existence of this efferent system (79), which had been suspected on the basis of earlier physiological findings (20). The origin of the efferent . system was, however, unknown, Since the cerebellum develops in very close relation with the stato-acoustic system and since a certain component of the vestibular projection to this center is direct in both lower (27) and higher vertebrates (2), it seems possible that the cerebellum has some direct action upon the peripheral organ. Occasionally we observed directcurrent potential changes at the frog vestibular organ following the stimulation of the auricular lobe; however, no clear physiological meaning has so far been attached to this finding. Although the functional significance of the cerebello-vestibular system has not been ascertained, this system may be inhibitory in nature, as is the olivocochlear bundle (22), particularly since Purkinje cells inhibit all target cells so far studied (4). The demon- stration of a direct cerebello-vestibular 1330 References and Notes 1.S. Ramon y Cajal, Histologie dui Systéme Nervoux de ’Homme et des Wértebrés (Maloine, Paris, 1911). 2. J. Jansen and A. Brodal, Cerebellar Anatemy (Johan Grundt Tanum, Oslo, 1954). 3. F. Walberg and J. Jansen, Exp. Neurol. 3, 32 (1961); R. P. Eager, J. Comp. Neurol, 120, 81 (1963). 4. M. Ito and M, Yoshida, Experientia 20, 515 (1964); Exp. Brain Res. 2, 330 (1966); M. Ito, M. Yoshida, K. Obata, Experientia 20, 575 (1964), 5. R. Llinds and J. F, Ayala, NeuropfAysiological Basis of Normal and Abnormal Motor Activities, M, D. Yahr and D. P. Purpura, Eds. (Raven Press, Hewiett, N.Y., 1967). 6. J. C. Eccles, R, Llinds, K. Sasaki, J. PAysiol. 182, 316 (1966). 7. R. Liinds and J. Bloedel, Science 155, 601 (1967). 8. R. Llinds, W. Precht, §S. Kitai, Brain Res., 6, 371 (1967). 9. J, C. Eccles, R. Llinas, K. Sasaki, J. Physiol. 182, 268 (1966). 10. R. Linds and J, Bloedel, Brain Res. 3, 299 (1966-1967). 11. J. C. Eccles, R. Llinads, K, Sasaki, Exp. Brain Res, 1, 82 (1966). 12. P. B. C. Matthews, C. G. Phillips, G. Rushworth, /. Exp. Physiol. 43, 39 (1958). 13. R. Granit and C. G. Phillips, J. Physiol. 133, 520 (1956). 14. P. Andersen, J. C, Eccles, P. E. Voorhoeve, J. Neurophysiol. 27, 1138 (1964). 15. D. Hillman, unpublished results. 16. G. L. Rasmussen and R. R. Gazek, Anat. Rec. 130, 361 (1958); A. E. Petroff, ibid, 121, 352 (1955), 17. J. Wersall, Acta Oto-Laryngol. Suppl. 126, 1 (1956); H. Engstrém, Acta Oto-Larynegoi. 49, 109 (1958). 18. O. Sala, Oto-Laryngol. Suppl. 197, 1 (1965). 19, L. Gleisner, P. G. Lundquist, J. Wersall, J, Ultrastruc. Res. 18, 234 (1967). 20. R. S. Schmidt, Acta Oto-Laryngol. 56, St (1963); L. Gleisner and N. G. Henriksson, Acta Oto-Laryngoi. Suppl. 192, 90 (1963). a1. O. Larsell, J. Comp. Neurol. 36, 89 (1923). 22. R. Galambos, J. Neurophysiol. 19, 424 (1956); J. Fex, Acta Physiol, Scand. Suppl. 189, 1 (1962); J. E. Desmedt and P, Monaco, Nature 192, 1263 (1961). 11 September 1967 n Erythrocyte Transfer RNA: Change during Chick Development Abstract, Radioactive aminoacyl transfer RNA’s isolated from erythrocytes in the blood of 4-day-old chick embryos and from reticulocytes of adult chickens were analyzed by chromatography on methylated albumin kieselguhr and freon columns, Embryonic and adult methiony] transfer RNA’s showed qualitative and quantitative differences in both chromatographic systems. The patterns for arginyl, seryl, and tyrosyl transfer RNA’s in the two cell types were similar, while the leucyl transfer RNA patterns suggested a difference. Structural modification of transfer RNA (tRNA) may play a regulatory function in cell differentiation and me- tabolism (7). With methylated albumin kieselguhr (MAK) chromatography, Kano-Sueoka and Suecka (2) demon- strated an alteration in leucyl-tRNA after bacteriophage T2 infection of Escherichia coli; this finding was confirmed by Waters and Novelli (3), using the reversed-phase chromatography developed by Kelmers et al. (4). Kaneko and Doi (5) found a change during sporulation of Bacillus subtilis in the elution pattern of valyl-tRNA from MAK columns. To look for changes in specific tRNA’s during development, we used avian immature red cells as a test system and compared the chromatographic profiles of aminoacyl-tRNA’s from red cells present in the blood of 4-day-old chick embryos and of reticulocytes of adult chickens. The techniques in this study were MAK (2) and freon columns (6). Of the five aminoacyl- tRNA’s examined, only the methionyltRNA gave a strikingly different elution pattern. Aduit chickens (White Leghorn) were made anemic by daily injection (for 3 days) of 15 mg of phenylhydrazine fin 0.14 tris( hydroxymethyl) aminomethane (tris) buffer, pH 7.2] and were bled on the 6th day. Eggs from the same strain were incubated at 37°C for 4 days, and blood cells were collected by bleeding the embryos. Blood cells from either source were washed twice with 0.145M NaCl, 5 x 10°*M KCl, and 0.0015M Megtl., and once with 0.14544 NaCl, 5 x 10°4*M FeCl, and 0.01M phosphate buffer (pH 7.4); 0.12 ml of packed embryonic cells was suspended in the latter medium supplemented with glucose (200 mg/ ml) with a total volume of 0.5 ml. For adult cells, 0.5 ml of packed cells was similarly incubated in a total volume of 2.0 ml. To cells previously incubated at 38°C for 10 minutes, MC. or 3H-labeled amino acid (5 to 10 wc) and the 19 remaining nonradio- active amino acids (1 ,»mole of each) were added. After incubation for an additional 12 minutes, cycloheximide (10°4M4) was added to inhibit protein synthesis (7) and thus prevent the transSCIENCE, VOL. 158