Blood Formation in Infancy: Part II.--Normal Erythropoiesis

There is general agreement that the fall in haemoglobin after birth is an expression of the increased oxygen saturation of the blood when lung replaces placenta as a source of oxygen.We have sought to express this idea concretely, to show that the changes which occur in the form and number of red cells after birth are due to variations in the erythropoietic activity of the marrow, and finally to infer that this activity is itself governed by the need to maintain the oxygen content of the blood at a constant level. Miterial and MethosThe material was the same as has been described in Part I, consisting of 105 samples of venous blood together with 102 bone marrow samples, taken from 25 infants from birth to 3 months.Our methods have been described in Part I.They were chosen after considering the following probable causes of the divergent results of previous authors in this field.Differences in haemoglobinometry may cause discrepancies, as may differences in methods of sampling.Skin prick samples of blood are apt to give variable results according to the site and depth of puncture, and tend to give higher values than venous samples, this effect being large in the first week of life (Vahlquist, 1941; DeMarsh, Alt and Windle, 1948; Oettinger and Mills, 1949).Consistent and reproducible results are most surely obtained by venous sampling, which was used exclusively in the present study.Differences in delay before clamping the cord may also affect results.Although DeMarsh, Alt and Windle (1941) list authors as far back as 1877 who have investigated the influence of this factor upon the post-natal blood picture, many subsequent studies have ignored it.Early clamping of the cord was the rule in this series.Differences in infants' growth rates, as Washburn DAYb F}G.1.-Changes in the red blood cels from birth to 3 months.214