300 American Quarterly Aficroscopical Journal. 



be either slightly or quite deeply colored. It would seem that the 

 haemoglobin is deposited as small granules in different parts of the 

 cells, to become evenly disseminated afterwards. 



At this time there are large, circular, oval, nucleated red blood- 

 corpuscles, identical with those seen as late as the middle period 

 of uterine life. They increase greatly by cell division, at least 

 until the embryo reaches a certain age, after which their multi- 

 plication may be due to other causes. 



The development of the red corpuscles in the adult is, and must 

 be, different from their embryonic origin. The basis upon which 

 this assertion rests must be stated, for it might be said that the 

 corpuscles in the adult are either the identical ones found in the 

 embryo, or that they are formed from these by cell division. 



The first statement cannot be true, for there is every reason to 

 believe that the red blood-corpuscle is exceedingly short-lived, 

 (see Foster's Physiology, 2d edition, p. 27.) The number of cor- 

 puscles in the blood varies greatly at different times, as is proved 

 by counting them. Again, after hemorrhage or disease, the normal 

 amount may be regained in a very short time. If the urinary and 

 bile pigments are derived from the haemoglobin, the number of red 

 corpuscles destroyed must be very great. The second assertion 

 cannot be true, for the corpuscles very seldom, if ever, increase by 

 cell division in the adult {IbiJ., p. 28). 



They must, therefore, have an origin entirely distinct from that 

 of the embryonic cells. 



One object of this paper is to strengthen an old theory and 

 answer some objections to it. 



If we take the pulp of the spleen and examine it carefully, 

 there may be seen some large, circular cells, colored with haemo- 

 globin. These cells are, perhaps, the protoplasmic cells of Kolliker. 

 Some of them contain in their interior, the remains of from one to 

 ten red corpuscles. The reason why these very large cells are not 

 found in the circulation, is probably because they are too large to 

 enter the venous capillaries (see below histology of the spleen). 

 Their large size is attained by appropriating to themselves, 

 through their amoeboid movements, the remains of one or more 

 red corpuscles; this operation must take place in the spleen pulp, 

 outside of the vessels. Their size will prevent them from entering 

 the first venous ca])illaries, until they have undergone cell divi- 

 sion. This division may be due to the same cause that keeps the 

 amoeba about an average size, viz. : the attraction of its constituent 



