614 XIII. HEMOGLOBIN AND PORPHYRIN SYNTHESIS 



2860); with regard to ascorbic acid the evidence is still considered 

 contradictory by some (1894,3103, cf. also 82, 511, 178 J^). 



There is suggestive, but not conclusive, evidence for the hemopoietic 

 activity of other vitamins. Mason and Mason {1880) found lack of thiamine 

 to cause a macrocytic hypochromic anemia in man {cj. also Jt.28), but Elvehjem 

 and co-workers {1795) observed no impairment of hemoglobin synthesis in 

 dogs bled regularly and supplied with the other vitamins of the B class. 

 According to Kornberg, Tabor, and Sebrell {2803) thiamine has only a very 

 slight effect on anemic rats. These workers found biotin inactive, but 

 Sydenstricker, Isbell, and co-workers {2723) cured the anemia caused by 

 egg white injury in man by biotin administration. Elvehjem and co-workers 

 {2391) increased the hemoglobin content of the blood of anemic dogs to 

 11-14 gram per cent by a synthetic diet containing other vitamins of the 

 B class without biotin, but found the latter able to cause a further increase. 

 Scott and co-workers {2523,252^) found pyracins in addition to folic acid 

 to hasten the recovery of the chicken from macrocytic anemia; this was not 

 confirmed by Luckey, Elvehjem, and co-workers {1786). A correlation of 

 2?-aminobenzoic acid to hemopoiesis has been postulated by Vannotti {2853) ; 

 this substance is a constituent of folic acid. It has also been claimed that 

 vitamins A and P are required for hemopoiesis. 



Some of the data on the significance of the vitamins of the B class must 

 be treated with reserve. Recent work has drawn attention to the importance 

 of bacterial synthesis of vitamins in the intestine, and the effect of a given 

 vitamin on hemopoiesis may be due to its function as an essential growth 

 factor for intestinal bacteria which produce some other vitamin actually 

 required for hemopoiesis. Some of the work will probably have to be repeated 

 when the interrelationships of the vitamins in the physiology of the host, the 

 microorganisms, and the symbiosis between the two are better understood. 



General inanition consequent upon vitamin deficiency may cause inhibi- 

 tion of hemopoiesis, and the effect of a particular vitamin on hemopoiesis 

 may have been caused in some instances by abolition of inanition rather 

 than by a particular effect on hemopoiesis. 



About the way in which the vitamins act on hemopoiesis and cyto- 

 poiesis we have little certain knowledge. 



Nicotinic acid, probably riboflavin, and possibly ascorbic acid act on the 

 respiration of red cells and are required for the maturation of the erythrocyte 

 rather than for the synthesis of hemoglobin. Nicotinic acid is required directly 

 for the synthesis of the coenzyme in the erythrocyte, for which nicotinamide 

 is far less effective {105,1124,1125,1295,1565,21^27). According to Handler 

 and Featherstone {1124) the lack of coenzyme in the immature red cell causes 

 arrest of its maturation at the primitive erythroblast stage. The anemia is 

 macrocytic; the mean corpuscular hemoglobin is slightly increased, but the 

 mean corpuscular hemoglobin concentration is decreased. The total circu- 

 lating hemoglobin is only 15% of the normal. Macrophages in the spleen 

 are filled with hemosiderin and iron-containing cells are also found in the 

 bone marrow. 



