THE RED BLOOD CORPUSCLES 877 



is very similar. In the red marrow are a number of nucleated cells con- 

 taining haemoglobin, which are thought by Lowit to be themselves derived 

 from colourless nucleated cells. In the confused medley of colourless cells 

 which are found in the bone marrow and are precursors of all the varied 

 corpuscles found in the blood, it is difficult to be certain of the identity 

 of the colourless erythroblasts and to distinguish them from the smaller 

 colourless cells engaged in bone formation or in the production of leuco- 

 cytes. The haemoglobin-containing cells are* often .to be seen in process 

 of division, and the nucleated daughter-cells appear to undergo a process 

 of nucleolysis, the nucleus being extruded or dissolved. When blood forma- 

 tion is quickened as the result of previous destruction or loss, some of these 





FIG. 377. Section of red marrow of pigeon. (DENYS.) 

 Ic, eosinophile leucocytes; eg, fat cells; e, nucleus of endothelial cell of 

 bloodvessel; ca, blood capillary; er, erythroblasts lying within vascular 

 endothelium ; glr, fully formed red corpuscles. 



immature nucleated blood discs may make their way into the circulation 

 and be found in the blood, where they are spoken of as normoblasts. 



How long a corpuscle continues to exist in the circulating blood is not 

 known. The experiments, made to determine the length of time during 

 which foreign corpuscles such as those of birds can be recognised after 

 injection into the circulation of & mammal, are evidently beside the mark, 

 since these foreign cells will be destroyed by the serum and rapidly taken 

 up by the phagocytes of the body. Sooner or later however, every cor- 

 puscle undergoes disintegration, a process which is generally ushered in 

 by the ingestion of the corpuscle by some phagocyte cells. Thus in the 

 haemolymph glands and in the spleen, we find large cells which have englobed 

 red corpuscles and in which we can recognise pigment granules derived 

 from their destruction. The chief place of disintegration of the haemoglobin 

 is certainly the liver, i. e. the organ where the haematin is converted into bile 

 pigment. Injection of haemoglobin into the circulation causes increased 

 secretion of bile pigment. A section of normal liver immersed in potassium 



