Magnitude and pattern of compensatory growth in rats after cold exposure.

It is a common observation that normal growth is affected or suppressed in young individuals by environmental adversities and physical disturbances. On the other hand, when health or favorable conditions are restored, the tempo of growth promptly accelerates as if the individual is trying to make up for the growth debt incurred. Tanner has referred to this increased growth rate after diseases or starvation as compensatory or 'catch-up' growth, a topic on which he has written eloquently and fully in a number of articles (1963a, b). He considers this compensatory growth as a 'self-stabilizing' or 'target-seeking' phenomenon in the regulatory control of growth. Growth of young rats is slowed by severe cold and increased by warmth (Heroux & Gridgeman, 1958; Chevillard, Portet & Cadot, 1963). The aim of the present investigation is to show the magnitude and pattern of compensatory growth in rats after single and repeated cold exposures; to evaluate age differentials in this response; and to study the pattern and relative rate of compensatory growth in the various bony segments of the appendages.