244 MANUAL OF PHYSIOLOGY. 



their nucleus, and assume the characteristic shape of the red cor- 

 puscles, the rest of the original mass of protoplasm remaining as 

 a rudimentary blood vessel. 



In the later stages of embryonic life the red corpuscles are said 

 to be formed in the liver, possibly out of protoplasmic elements 

 which are made in the spleen and thence carried to the liver by 

 the portal circulation. 



In the connective tissue of rapidly growing animals tadpole 

 (Kolliker), rabbit (Ranvier), rat (Schafer) certain cells can be 

 seen to be connected in the form of a capillary network, and within 

 the protoplasm of these cells red coloring matter is developed, and 

 the particles of color can soon be recognized as characteristic 

 blood corpuscles, arranged in rows within the newly-formed net- 

 works. Thus isolated, small networks of capillaries, consisting 

 of a few meshes filled with blood corpuscles, are formed inde- 

 pendently of the general circulation. 



These corpuscles and their haemoglobin are manufactured by 

 isolated protoplasmic elements in the connective tissue, and sub- 

 sequently added to the general mass of blood by the growth of 

 the network bringing it into continuity with the neighboring 

 vessels. 



In the adult the formation of red blood corpuscle? is, of course, 

 much less active, but certainly never ceases to take place in 

 health, for the corpuscles must be renewed as they become worn 

 out, and incapable of performing their function. This reproduc- 

 tion can go on with considerable rapidity, as we see after severe 

 hemorrhage, when the normal richness in haemoglobin and cor- 

 puscles is soon arrived at. Their formation is, however, probably 

 confined to a few special organs spleen, liver, red medulla of 

 bones where transitional forms are found in such numbers as to 

 point to the probability of the red corpuscles being the offspring 

 of the colorless cells, whose protoplasm either manufactures anew 

 or collects the necessary haemoglobin, and then loses its nucleus 

 and ordinary cellular characters. 



We can only guess at the fate of the disks, but there are many 

 things which point to the spleen as the organ in which they are 

 destroyed. In the spleen an enormous number of protoplasmic 



