yt amar ous system comes to us from the cerebral process, which is induced through sense organs. On the other hand we receive through the resolving power re automated. As a result, the desired success is achieved with more speed and more precision, and mechanisms of great complexity are mastered. of receptive systems information about the environmental source of stimulation. In visual perceptions derived from both eyes, for example, paralactic shift is utilized in composing an integrated stereo image. The impression that the sensory stimulation originates in the en- vironment is confirmed through the di- rected motor reaction—for example, through the grasping of a visually localized object. The successful attempt to grasp the object confirms the correlation between perception and reality. Involved are consistent temporal and spatial relationships which produce the impression of causality (29). Simple mechanisms for the preservation of life are genetically controlled and subject to phylogenetic selection. Important individual behavioral patterns are determined prenatally. Complex reactions, on the other hand. are learned postnataliy, and their release is under the control of conscious will. Through frequent repetition, psychic functions become partially or totally Summary This article is based upon data which are suitable for the correlation of behavioral research and experimental neurophysiclogy. Causal thinking manifests a sort of integrative activity which brings simultaneous and successive patterns of nervous excitation into a subjectively meaningful frame of reference. While neuronal patterns determine the content of consciousness, they fail to provide clues concerning the transformation of such patterns into subjective experience. References and Notes 1. C. J. Herrick, The Evolution of Human Nature (Univ. of Texas Press, Austin, 1956). 2. The Neuropsychology of Lashley (selected papers of K. 5. Lashley), F. A. Beach, D. O. Hebb, C. T. Morgan, H. W. Nissen, Eds. (McGraw-Hill, New York, 1960). 3. D. O. Hebb, The Organization of Behavior (Wiley, New York, 1949). 4, W. Penfield and T. Rasmussen, The Cerebral Cortex of Man (Macmillan, New York, 1950). 5. H. Kiliver. J. Lancet 72, 567 (1952); : in Ciba Foundation Symposium on the Neurological Basis of Behavior, G. E. W. Wolstenhoime and C. M. O’Connor, Eds. (Little, Brown, Boston, 1958), p. 175. 6. D. W. Ploog, Jahrb, Max-Planck-Ges. (1963), p. 130; P. D. MacLean, Animal Behaviour 11, 32 (1963). 7, J, M. R. Delgado, Intern, Rev. Neurobiol. 6. 349 (1964). 8. P. D. MacLean, Psychosomart. Med. 11, 338 (1949): A.M.A. Arch. Neurol. Psychiat. 78, 113 (1957). 9. S. L. Polyak, The Vertebrate Visual System (Univ. of Chicago Press, Chicago, 1957). 10. R. Jung, in The Visual System, R. Jung and H. Kornhuber, Eds. (Springer, Berlin, 1961), p. 410. 11. D. H. Hubel and T. N. Wiesel, f. NeuroPhysiol, 28, 229 (1965). 12. G, Baumgartner, in The Visual System, R. Jung and H. Kornhuber, Eds, (Springer, Berlin, 1961), p. 296. 13. B. J. Alpers, Res. Pub. Ass. Nervous Mental Diseases 20, 725 (1940). 14. B, Andersson, Acta Physiol. Scand. 28, 188 (1953); , P. A. Jewell, S. Larsson, Ciba Foundation Symposium on the Neurological Basis of Behavior (Little, Brown, Boston, 1958), p. 76: B. K. Anand and J. R. Brobeck, Yale J. Biol. 24, 123 (1951). 15. W. R. Hess, Diencephaion, Autonomic and Extrapyramidal Functions, O. Krayer, Trans. (Grune & Stratton, New York, 1954); and M. Briigger. Helv, Physiol. Pharmacel. Acta 1, 33 (1943); R. W. Hunsperger, ibid. 14, 70 (1956). 16. B. Andersson and W. Wyrwicka, Acta Physiol, Scand. 41, 194 (1957). 17. W. R. Hess, The Biology of Mind (Univ. of Chicago Press, Chicago, 1964). 18. W. A. Stoll, Schweiz. Arch. Neurol. Neurochir, Psychiat. 60, 1 (1947). 19. W. R. Hess, Psychologie in Biologischer Sicht (Thieme, Stuttgart, ed. 2, 1967). 20. The work discussed was supported by a grant from the Swiss National Foundation of Scientific Research. 1500 instances of laboratory-acquired infections resulting in 39 deaths. A standing Committee on Laboratory Infections and Accidents of the Ameri- can Public Health Association (APHA Arbovirus Infections of Laboratory Workers /CLIA) (3) has maintained a file of cases of laboratory-acquired infections whether reported to the public or by Extent of problem emphasizes the need have been over 2700 cases with 107 fatalities. for more effective measures to reduce. hazards. R. P. Hanson, S. E. Sulkin, E. L. Buescher, W. McD. Hammon, private communication; so far, there Molecular biologists interested in the relation of viruses to the metabolic systems of cells and in the structure of their nucleic acids may now be added to the many virologists who have long worked with a heterogeneous group of viruses known as_ arboviruses. The health hazard inherent in the manipulation of these viruses may ruses. The magnitude of the overall not be well known to many of the problem of laboratory-acquired infecnewer investigators who lack clinically tions, however, became evident in an exoriented training. tensive survey (2) which revealed over The arboviruses, a contraction of R. W. McKinney, and T. H. Work Prior to 1950, only an occasional report was concerned with the need for protection of laboratory personnel who came in daily contact with disease-producing agents. Sulkin and Pike (/) had collected data on viral infections contracted in laboratories in the hope that this information would be helpful in determining where the greatest caution must be exercised in working with vi8 DECEMBER 1967 The authors are members of the American Committee on Arthropod-borme Viruses/Subcommittee on Laboratory Infections (ACAV/SLI). Dr. Hanson is in the department of veterinary science, University of Wisconsin, Madison; Dr. Sulkin is in the department of microbiology, University of Texas Southwestern Medical School, Dallas; Dr. Buescher is in the department of virus diseases, Walter Reed Army Institute of Research, Washington, D.C.; Dr. Hammon is in the department of epidemiology and microbiology, University of Pittsburgh, Pittsburgh, Pennsylvania; Dr. McKi me) . is at Ft. Detrick, Frederick, Maryland; Dr, Work is in the department of infectious and thople ? diseases, University of California School of Public Health, Los Angeles. 1283