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Human brains were removed at autopsy and examined grossly and histologically for any abnormality or evidence of disease. Sixty-two brains appearing normal by these criteria were examined further. First, a detailed record of alcohol consumption was obtained. Second, frozen punches of gray and white matter were used to determine the compositional change associated with age and drinking patterns. Increased age was associated with an increase in the water content, particularly in the white matter, a decline in RNA content in gray matter, a decline in total protein in white matter, and a decline in both myelin and the myelin-like subfraction. The loss of myelin membrane in white matter corresponded to a similar increase in water content, although there was an additional loss of some nonmyelin protein. There was no significant shift in the density between the myelin and the myelin-like membranes, and the protein composition of myelin was not significantly altered by age. A history of heavy alcohol consumption was associated with a relative increase in total protein in white matter even though heavy drinking accelerated the age-related loss of myelin. Presumably, alcohol produced a lag in the rate at which nonmyelin proteins are lost or accelerated the accumulation of abnormal protein. Alcohol consumption did not influence the myelin composition or the ratio of myelin and myelin-like membranes. The interval between patient death and autopsy was shown to have little or no effect on the samples used in this study. These data show that normal aging, uncomplicated by other disease processes, can have a significant effect on the composition of brain tissue, particularly the white matter, and that heavy alcohol consumption accelerates degenerative change, even in tissue appearing normal by histology.

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One hundred fifty-six male C57B1/10 mice lived in groups of 1, 4, 8, 16, or 32 animals. For all group sizes animals were housed either in cages of a constant size, so that group size and crowding correlated, or were housed in cages with floor space varied proportional to the group size. Closed-maze exploration decreased with increased group size, irrespective of crowding, while wheel activity was an interactive effect of group size and degree of crowding. Reduced concentrations of brain protein and nucleic acids accompanied living in larger groups, whether crowded or not, but rate of intracellular synthesis of RNA and protein by DNA was more dependent upon the size of the living space.*A portion of the data reported here is also reported in an unpublished master's thesis by C. E. Miller, Population density and overcrowding: Possible confounding due to space. Northern Illinois University. 1969.2 Requests for reprints should be sent to R.