ANATOMICAL ELEMENTS. 11 



opment of the foetus and in the adult, it is probable that the red marrow of 

 the bones and, perhaps, to a certain extent, the spleen have important uses in 

 connection with the development of the red blood-corpuscles. The observa- 

 tions of Neumann, of Konigsburg, and of Bizzozero, of Turin, about the 

 year 1868, have been extended and confirmed by others, and show that there 

 is a generation of red corpuscles in the red marrow .of the bones, which is 

 now regarded as the most important of the so-called corpuscle-forming organs. 

 In the foetus and in the young infant, the marrow of nearly all the bones is 

 red, or of the kind called lymphoid. In the adult, the marrow of the long 

 bones is yellow, or fatty, the red marrow being confined to the cancellated 

 structure of the short and the flat bones. Although the researches with re- 

 gard to the spleen are less positive and definite in their results, it is proba- 

 ble that this organ also contributes to the development of the red blood- 

 corpuscles. 



The exact mode of development of the red corpuscles in the marrow and 

 in the spleen has not been very satisfactorily described and is still a question 

 concerning which there is much difference of opinion among histologists. 

 A full discussion of this question would be out of place in this work, which 

 is intended to embrace only those points in histology that have been defi- 

 nitely settled. 



It is probable that the red corpuscles are, in certain number, destroyed 

 in the passage of the blood through the liver and perhaps, also, in the spleen, 

 the coloring matter contributing to the formation of the biliary and the urin- 

 ary pigmentary matters. If this view be accepted, the spleen is concerned 

 in both the formation and the disintegration of blood-corpuscles. 



In the present state of knowledge, the following seem to be the most 

 rational views with regard to the development and destination of the red 

 blood-corpuscles. 



1. At the time of their first appearance in the ovum, the blood-corpuscles 

 are formed by no special organs, for no special organs then exist. 



2. In the foetus, after the development of the marrow of the bones and of 

 the spleen, and in the adult, these parts have important uses in the forma- 

 tion of the red corpuscles, especially the red marrow of the bones. 



3. It is probable that the red blood-corpuscles are constantly undergoing 

 destruction, and that their coloring matter contributes to the formation of 

 other pigmentary matters. As the corpuscles are thus destroyed, and as they 

 are diminished in number in disease or by haemorrhage, they are probably 

 replaced by new corpuscles formed in greatest part in the red marrow of the 

 bones. 



4. Pathological observations seem to show that in certain cases of anae- 

 mia, when there is an abnormal destruction of red corpuscles, the activity of 

 the corpuscle-forming office of the marrow is increased, compensating, to a 

 certain extent, the conditions which involve the abnormal destruction of the 

 corpuscles. 



Uses of the Red Blood- Corpuscles. Although the albuminoid constitu- 

 ents of the plasma of the blood are essential to nutrition, the red corpuscles 



