No. I.] BLOOD CORPUSCLES. 



109 



resemble exactly the lymphocytes, and may be regarded as 

 lymphocytes newly arrived in the circulation and as yet un- 

 changed in structure (Erb, Lowit). These are characterized 

 physiologically, as was pointed out some years ago by Schultze 

 (45), by not possessing the power of making amoeboid move- 

 ments, A second form of uninucleated leucocyte is character- 

 ized by its large, finely granular, protoplasmic envelope. This 

 form is amoeboid, and it seems most reasonable to suppose that 

 it is derived from the first form, or lymphocyte, since this 

 latter cell is the only or chief form in which the leucocytes of 

 the lymph enter the blood. The first variety of uninucleated 

 leucocyte passes into the second in consequence of a growth 

 in the cell protoplasm while in the blood current, the proto- 

 plasm meanwhile acquiring the power of contractility. A third 

 variety of uninucleated leucocyte, and what seems to repre- 

 sent a third stage of development, is like the last, except that 

 the nucleus is no longer oval or spherical, but is drawn out to 

 an elongated strap shape, and may take either a horse-shoe 

 form or may be more or less coiled into a spiral. This form 

 of cell is especially abundant in the cat's blood, and possesses 

 the most active amoeboid properties. The origin and meaning 

 of the multinucleated forms has been for some time a subject 

 of dispute among histologists. Formerly it was generally 

 thought that they represented cells in process of multiplication 

 by direct division ; and this view is still warmly supported by 

 Arnold and others. The normal fate of the multinucleated 

 cell, according to this view, is to divide into a number of cells 

 corresponding to the number of nuclei. Others, and especially 

 Lowit (29), have urged that the multinucleated forms are cells 

 on the way to disintegration, and the so-called nuclei are made 

 simply by the fragmentation of the nucleus of a uninucleated 

 leucocyte, and represent the first step in the process of de- 

 struction. As far as my observations go, they support Lowit's 

 view. I have never seen any indication of the multinucleated 

 cells segmenting to form new cells. On the contrary, there is 

 every reason to believe that they are undergoing a course of 

 retrograde changes, the normal termination of which will be 

 the disintegration and dissolution of the cell. With reference 

 to the derivation of the multinucleated forms from the uni- 

 nucleated by fragmentation of the nucleus, I have been able 



