M. J. KARVONEN 



In order to investigate whether it was necessary to assume the 

 presence of an unusually soluble new Hb, or whether the anomalously 

 high solubilities were due to some interactions of the foetal and adult 

 Hb's, artificial mixtures of adult and foetal Hb were made. It was 

 found, that the anomalous solubilities observed in the samples from 

 the transition period could be closely reproduced by making suitable 

 artificial mixtures of foetal and adult Hb. The atypical solubility of 

 the mixtures was paralleled by irregularities in the solid phase. There 

 was, therefore, no necessity to introduce a new Hb, and, on the basis 

 of the observed analogies, the transition could be simply ascribed to 

 a gradual intermixture of the foetal with the adult type of Hb. 



By using a suitable procedure, one could achieve a partial separation 

 of the foetal and adult type Hb's from the transition samples, but 

 completely pure fractions were not obtained with the applied methods. 



As the artificial and naturally occurring mixtures of adult and 

 foetal Hb showed interactions affecting their solubility, no simple 

 solubility method could be used for estimating the percentage of the 

 components. An attempt was made, however, to use the observed 

 solubilities of the artificial mixtures at two widely different /jH's for 

 assessing, purely empirically, the approximate composition of the 

 samples from the transition period. This method can by no means 

 be regarded as an exact one, as neither of the components of the 

 artificial mixtures evidently is a single substance. If the mixtures were 

 composed of only two proteins, then theoretically, of course, even the 

 anomalous solubilities ought to be thermodynamically strictly de- 

 termined. Several series of artificial mixtures were made. On the 



100 



JO 



60 



130 O 

 Days 

 Foetal Age Post-natal Age 



Figure 5. The approximate composition 

 of the Hb during late foetal and early 

 post-natal life, as based on the analogous 

 solubility of the artificial mixtures. 

 Each vertical line represents the limits 

 of the composition of each sample. 



284 



