No. I.] BLOOD CORPUSCLES. 07 



segmented or notched in the way described by Kolliker (?) and 

 Neumann, and interpreted by them as an indication that the 

 process of absorption had begun. Nevertheless, I have seen 

 nuclei of this character already partially extruded from the 

 cell, showing that the partial fragmentation of the nucleus is 

 not conclusive proof that it is in process of absorption. To 

 show that the escape of the nucleus is a normal and constant 

 phenomenon we have the following facts : 



In specimens of the marrow of kittens and adult cats, espe- 

 cially after repeated bleedings, and also in the blood-forming 

 organs of the embryo when teased out in their own serum and 

 stained with methyl green, one can easily find very many 

 examples of nucleated red corpuscles in the act of losing their 

 nuclei. In some animals the number of examples is striking 

 — a dozen or more may be seen in a single specimen ; while at 

 other times, especially in unbled animals, it may be difficult to 

 find a single example. But in bled animals, especially bled 

 kittens, in which it is fair to suppose that the process of blood 

 formation is greatly accelerated, no difficulty will be found in 

 obtaining a number of examples showing all the steps in the 

 act of extrusion, from the time when the nucleus has only an 

 eccentric position up to the period when it lies completely 

 outside the cell, as shown in Fig. 2. The frequency with 

 which this phenomenon occurs, especially when the production 

 of red corpuscles is increased, requires that it should be ex- 

 plained. Now it must be a normal occurrence, or else it comes 

 from the action of the reagents, or possibly it is the result of 

 post-mortem changes taking place in the cell after removal 

 from its normal environments. 



There are a number of facts which may be adduced to show 

 that the phenomenon is not an accidental or post-mortem 

 change, but a normal occurrence. In the first place, most of 

 the specimens were obtained from pieces of the marrow (or liver 

 in the embryo) which were taken as quickly as possible from 

 the animal after killing, and treated with methyl green, so that 

 only a few minutes intervened between the death of the animal 

 and the action of the methyl green. This reagent, as is well 

 known, is an excellent fixative. It preserves fairly well the 

 nuclear figures of karyokinesis, and fixes the blood plates quite 

 as well as osmic acid. It is not likely, then, that such a re- 



