554 SAMUEL H. HURWITZ 



metabolism of hemoglobin and the blood-derived pigments, .with a discus- 

 sion of the regulatory influence of the spleen, liver, and bone-marrow 

 and the effects of various diets on the decomposition and formation of 

 hemoglobin. To these subjects much new and valuable knowledge has 

 been added within recent years, and it is not unlikely that some of the 

 results will have an important bearing upon the treatment of blood 

 diseases in man. 



Mechanism of Blood Destruction and Regeneration. The Destruc- 

 tion of Red Blood-Cells. It has long been recognized that in the healthy 

 body there is a constant disintegration and regeneration of red blood- 

 corpuscles. The exact rapidity with which this takes place and just 

 where and how this destruction occurs are questions which still await 

 solution. Estimates based mainly upon the daily excretion of the hemo- 

 globin-derived pigments indicate that under normal conditions from one- 

 tenth to one-fifteenth of all the corpuscles in the body are lost and re- 

 placed in twenty-four hours (Rons and Robertson (a) ( &) ). Judged by such 

 calculations, the average life of the erythrocyte would be from ten to fif- 

 teen days. More recent work, however (Whipple and Hooper(c)), by 

 proving that bile-pigments may have other sources than red blood-cells, has 

 demonstrated a large possible source of error in such calculations. In 

 fact, evidence gained by means of differential agglutination of red cor- 

 puscles in vitro would seem to show that the life cycle of the transfused 

 corpuscle is at least thirty days (Hunter, W.(a) ; Ashby). 



The literature on the normal methods of destruction of the red blood- 

 cells is extensive, but inconclusive. As has been pointed out, two separate 

 processes may be at work (Hunter, W. K. (d)). But more recent studies 

 have established a third mode of red blood-corpuscle destruction. 



The first mode of disposing of the erythrocytes is through the phago- 

 cytic activity of certain cells (erythrophages). Certain facts concerning 

 this process have been well established. It is known that large endothelial 

 cells in the spleen take up red blood-cells and destroy them and that blood- 

 pigment is sometimes present in the Kupffer cells of the liver, indicating 

 that they play a part in the destruction (Pearce and Austin). Under 

 certain conditions, moreover, the lymph glands and the bone-marrow may 

 perform a like function. That these erythrophages remove badly dam- 

 aged or decrepit red corpuscles from the circulating blood under pathologi- 

 cal conditions is evidenced by the increased amount of detritus which they 

 contain after the action of substances which injure red blood-cells. 

 Whether, in addition, these cells may play an active part in blood destruc- 

 tion by attacking and destroying relatively healthy cells is still open 

 to question. 



While some investigators hold that phagocytosis is of itself sufficient 

 to account for blood destruction, Rous and Robertson (a) (&) as a result of 

 their careful experimental studies, are inclined to the view that in man 



