32 A MANUAL OF PHYSIOLOGY 



capillary bloodvessels. At the same time clumps of nuclei, 

 formed by division of the original nuclei of the cells, gather 

 at the nodes of the network. Around each nucleus clings a 

 little lump of protoplasm, which soon develops haemoglobin 

 in its substance ; and the new-made corpuscles float away ' 

 within the new-made vessels. In later embryonic life the 

 nucleated corpuscles seem in part to be developed in the 

 liver, spleen, red bone-marrow, and the blood itself by 

 division of previously existing nucleated corpuscles, in part 

 to be formed endogenously within special cells in the liver, 

 spleen, and perhaps the lymphatic glands. 



In the mammal in extra-uterine life the chief seat of 

 formation of the red blood-corpuscles seems to be the red 

 marrow of the bones of the skull and trunk, and of the ends 

 of the long bones of the limbs. For a short time, however, 

 after birth the formation of non-nucleated corpuscles may 

 still go on in other situations, as in certain cells in the 

 omentum of the rabbit (Ranvier), and in the subcutaneous 

 connective-tissue corpuscles (Schafer); while at anytime the 

 spleen (Bizzozero and Salvioli) in dogs and guinea-pigs, and 

 probably other organs, may in emergency for instance, 

 when the number of blood-corpuscles has been seriously 

 diminished by haemorrhage take on a blood-forming func- 

 tion. In the red marrow special nucleated, feebly amoeboid 

 cells, originally colourless or nearly so, multiply by karyo- 

 kinesis or indirect division, and are transformed by various 

 stages into the ordinary non-nucleated red corpuscles, which 

 are washed away in the blood-stream. These blood-forming 

 cells have received the name of erythroblasts or haemato- 

 blasts. 



A constant destruction of red blood-corpuscles must go 

 on, for the bile-pigment and the pigments of the urine are 

 derived from blood-pigment. The bile-pigment is formed in 

 the liver. It contains no iron ; but the liver-cells are rich 

 in iron, and on treatment with hydrochloric acid and 

 potassium ferrocyanide, a section of liver is coloured by 

 Prussian blue. Iron must, therefore, be removed by the 

 liver from the blood-pigment or from one of its derivatives ; 

 and there is other evidence that the liver is one of the places 



