60 STUDIES IN ADVANCED PHYSIOLOGY. 



tissue cells in which by a nuclear division they were formed, 

 elongate very rapidly and soon touch similar elongations of 

 neighboring tissue cells. Where they touch, the partition 

 dividing them melts away and the cavities of the cells are 

 converted into a system of capillaries. This system of 

 capillaries is soon connected with larger blood vessels and 

 so these nuclei find themselves in the general circulation 

 at once. The protoplasm of the tissue cell becomes liqui- 

 fied and helps to form the plasma of the blood. This 

 intra-cellular mode of development of red blood corpuscles 

 does not continue after birth, unless it be in animals such 

 as the rat, which are born in a very immature condition. 

 For this reason we must in the adult body seek for their 

 origin elsewhere. 



It is now fairly well established that in adult life they 

 arise in the red marrow of the bones. In this red marrow 

 there may be observed corpuscles which seem identical with 

 the nucleated red corpuscles of the embryo. In fact, it 

 seems probable that the nucleated embryonic corpuscles 

 migrating into the red marrow of the bones have been the 

 lineal ancestors of the nucleated red corpuscles in the adult 

 marrow. These corpuscles seem to divide like ordinary 



< Q fe 



Fig. 13. H^EMATOBLASTS IN PROCESS OF DIVISION. From the red marrow of the Guinea- 

 pig. (After Schafer.) 



corpuscles, possess the power of amoeboid movement, and 

 differ from the ordinary white corpuscles apparently in little 

 more than the possession of the haemoglobin. These 

 nucleated red corpuscles form the ordinary non-nucleated 

 corpuscles of the blood by having the nucleus gradually 

 atrophy and disappear. In fact, according to some observ- 

 ers the nucleus is said to be extruded from the corpuscle 

 and then dissolved, while the non-nucleated body is carried 

 away by the blood stream as a newly created blood cor- 

 puscle. These marrow corpuscles have been called ery- 



