The relation of weight of haematopoietic marrow to body weight.

Adequate evaluation of the effects of external radiation fields on the haematopoietic system often requires knowledge of the number of grams of active marrow which received specific radiation doses rather than the average dose to the entire active marrow. There are several published reports of the amount of active marrow in different bones expressed as fractions of the total active marrow in the body, but none in which the actual number of grams can be computed for the individual patient. In the present study the number of grams of active marrow in the individual bones of the head and torso of adults has been computed and expressed as percent of body weight. Differences between males and females are not significant. For the major bones of caucasians the standard deviations are less than 25%. Very limited data indicate that there may be a similar range for Japanese adults. Similar computations for children have not been attempted here because of the uncertainties in the necessary data on body proportions.