630 XIII. HEMOGLOBIN AND PORPHYRIN SYNTHESIS 



observations of Seggel, showing that the number of fluorescytes 

 increases with absolute or relative iron deficiency (Chapter XII, 

 Section 3.2.2.), are good evidence for this. 



Porphyrins are frequently found at the site of hemopoiesis, i.e., 

 the bone marrow in the adult, for instance in pernicious anemia. 

 The evidential value of these observations has been emphasized by 

 Thomas {2798), and they certainly support the hypothesis of por- 

 phyrin formation in hemoglobin synthesis. Nevertheless, as isolated 

 facts, they do not completely rule out porphyrin formation by abnor- 

 mal hemoglobin breakdown, since hemoglobin breakdown to bile 

 pigments occurs in the bone marrow. In pathologic conditions, por- 

 phyrins have been observed in the liver {322,558,685,2839,2850). In 

 some instances, this may be connected with extramedullary hemo- 

 poiesis, which has been observed by Fischer in the porphyria patient 

 Petry. 



7.2. Porphyrin Formation in the Embryo 



The formation of porphyrin in the incubated egg was first studied by 

 van den Bergh and Grotepass {228). The protoporphyrin of the egg shell 

 does not penetrate into the interior. An increase of the porphyrin in the 

 albumin, not in the yolk, was observed after about five days. Van den 

 Bergh concludes that the porphyrin cannot be derived by breakdown of 

 hemoglobin from the small amount of blood present at this period. Although 

 this conclusion is undoubtedly correct, it was based on a dubious comparison 

 between the ratio of porphyrin to hemoglobin in the egg and that in normal 

 adult blood. 



In a later study Sch0nheyder {2458) comes to conclusions similar to those 

 of van den Bergh. A simultaneous rise of coproporphyrin and hemoglobin 

 begins at the third day of incubation, hemoglobin rising to 19 mg., copro- 

 porphyrin to 7.5 ju,g. on the ninth day. These data show that the quanti- 

 tative relations do not actually exclude formation of porphyrin by break- 

 down of hemoglobin; the fact that the coproporphyrin is of type I, however, 

 shows that this assumption cannot be correct. Sch0nheyder concludes that 

 his results indicate an entirely independent synthesis of coproporphyrin and 

 of hemoglobin. This assumption is, however, unnecessary; his results are 

 equally well met by a theory in which coproporphyrin is derived as a by- 

 product of hemoglobin synthesis, but which provides for a variation of the 

 ratio of the isomerides {cf. Section 8.). 



Porphyrins do not enter the mammalian fetus from the mother (Frankel, 

 939; Hammer, 1111; cf. also 1691). Porphyrin is found in blood and bone 

 marrow of fetuses (Borstand Konigsdorffer, 322). The porphyrin content of 

 the fetal serum is 8-10 microgram per cent, and decreases to 1-3 microgram 

 per cent at birth. Fetal red cells also contain 2-3 times as much proto- 

 porphyrin as the adult erythrocyte (van den Bergh and Hijmans, 231). 

 Fikentscher's finding {758) that the porphyrin deposited in the fetal bones i? 



