THE RED BLOOD CORPUSCLES 195 



Hemochromogen in acid solution has four bands and, in alkaline solution, 

 two bands. One of the latter is dark and is situated between the D- and £'-lines, 

 while the other is less intense and covers the ^-line. 



Acid hematin possesses a sharply defined absorption band between the C- and D- 

 lines, the position of which varies somewhat with the type of the solution employed. 

 A second band, much broader but less intense, is present between the D-and F-lines. 

 By proper dilution this band may be converted into two. The one nearest the F-line 

 is dark and broad, and the one nearest E, light and narrow. Another very faint 

 band may be made out near D by diluting the liquid still further. Hematin in 

 alkaline solution presents one broad absorption band located principally between 

 the C- and D-lines, but extending slightly into the space to the right of D. 



On addition of a few drops of hydrochloric acid, an alcoholic solution of hema- 

 toporphyrin presents two bands, namely, one near D which is narrow and faint, and 

 one between D and E which is broad and sharply outlined. A dilute alkaline 

 solution of this substance presents four bands, namely, one between C and D, one 

 between D and E and covering D, one between D and E and very close to E and 

 lastly, one near F. With the aid of an alkaline zinc chlorid solution these bands 

 may be made to coalesce into two, namely, into one located at D and one situated 

 between D and E. In acid solutions this substance frequently shows four 

 bands, but much depends upon the manner in which the solution is prepared. 



THE LIFE HISTORY OF THE RED CORPUSCLES 



In the embryo the red cells originate in the so-called vascular 

 area. The blood-vessels appear at this time as a network of solid 

 threads, differentiated from the adjoining tissue by a greater opacity. 

 Their walls are made up of masses of cells which are intermingled 

 with ameboid corpuscles and of cells which possess a peculiar branched 

 appearance. Later on, when fluid has forced its way into the different 

 tubules from without, the cells on the outside arrange themselves in 

 the form of an endothelial lining, while loose clusters of large globular 

 cells project from here into the lumen of the vessel. All these cells 

 multiply very rapidly by indirect division. The cytoplasm of those 

 fastened to the inside wall is colorless and nucleated at first, but 

 gradually acquires a certain quantity of hemoglobin. These cells 

 become yellowish in color and eventually separate to assume a position 

 in the fluid within the channel. Being still in possession of a nucleus, 

 they are capable of multiplying by indirect division. Later on, how- 

 ever, as the individual tubules acquire a larger size and begin to anas- 

 tomose with one another, these newly developed cells, in which we 

 recognize the red corpuscles, migrate into the general circuit and hence- 

 forth lead an independent life. 



During the later stages of embryonic development, other organs 

 enter into the formation of these elements. To begin with, this func- 

 tion is centralized in the liver; subsequently, however, the spleen, 

 lymphatic tissues and red marrow of the bones take part in their 

 production. During the last periods of embryonic existence the im- 

 portance of the liver and spleen as corpusple-f orming organs decreases 

 very markedly, while that of the bone marrow increases steadily 

 until the end of fetal life. 



