T H E Restoration of Lost Organ Tissue* the Rate and Degree of Restoration by T. Addis, M.d., and W. Lew

When the usual relations that exist between organ weight and body weight are altered by the removal of part of an organ, a complete or partial restoration occurs in certain organs but not in others. In mammals the removal of a limb, an eye, or part of the brain is followed by no restoration. When one Cowper's gland is removed the remaining gland grows no larger (1) and, as we shall show in this paper, the excision of one seminal vesicle, half of the prostate gland, or one uterine horn does not cause any very appreciable change in the part that remains. But when we remove one testicle we find there is a slight increase in the weight of the remaining organ, a greater increase is seen when half of the total suprarenal (2) or ovarian (3) or renal tissue (4) is removed, and when part of the liver (5) or lung (6) is excised there is a complete restoration of the lost tissue. Compensatory hypertrophy is the term commonly used to cover all these instances of organ increase after loss of tissue but, even at the cost of breaking with usage it seems to us preferable to employ merely descriptive words and say that what happens in all of these organs is a restoration of lost tissue. That is all that our present knowledge warrants. "Hypertrophy," in the histological sense, is never all that occurs for there is always hyperplasia and in some cases there may be no hypertrophy. "Compensatory," since it implies a knowledge we do not possess, is a word that tends to still questioning as to the mechanism of organ restoration. That is unfortunate because with more knowledge might come the capacity to intervene in clinical situations in which the rate and degree of restoration of organ tissue lost through disease may be a matter of great moment. In this paper we give data on the relation between the growth rate of intact organs and the growth rate of organs whose total mass had been halved by operative removal. We assume that the increase that occurs in the remaining organ when one of a pair is removed is due to growth. We