gS HOWELL. [Vol. IV. 



agent would cause in one of the cells of the marrow an expul- 

 sion of the entire nucleus, and in others preserve the delicate 

 karyokinetic figures ; and, on the other hand, the fact that 

 the marrow was submitted to the action of the reagent so 

 quickly after the death of the animal, probably before the 

 death of the marrow cells, precludes the possibility of post- 

 mortem changes of the nature required to expel the nucleus 

 from a cell. So in several cases, both in the adult and the 

 kitten, after severe bleeding, and also in the foetus, I have 

 found examples of extruding nuclei in the circulating blood. In 

 these cases, the drop of blood was taken from the living animal 

 and mixed at once with the methyl green, so that there was 

 no opportunity for post-mortem changes (see Fig. 2). More- 

 over, I have obtained cases of extrusion frequently in sections 

 of marrow which had been taken from the animal as quickly 

 as possible after bleeding, and hardened in mercuric chloride. 

 Here, again, we have an excellent fixative quickly applied, 

 which ought to have prevented post-mortem changes on the 

 one hand, and on the other should not have acted with such 

 violence upon one of the kinds of cells found in the marrow 

 as to force out the nucleus. To adopt either one of these hy- 

 potheses to explain the extrusion is not permissible in the light 

 of our knowledge of the action of this reagent on cells in 

 general. 



In the second place, all the red corpuscles which I have seen 

 with the nuclei extruding belong to the class of mature nucle- 

 ated red corpuscles. Never have I seen a nucleus extruding 

 from a nucleated red corpuscle which showed a nuclear net- 

 work. This indicates that the escape of the nucleus is not 

 owing to any accidental or post-mortem changes, since there is 

 no reason under such conditions why all kinds of nucleated red 

 corpuscles should not have been affected in the same way. It 

 shows, also, that the extrusion of the nucleus is the normal 

 end to the life history of the nucleated red corpuscle, since it 

 is found only among those which seemed to have reached full 

 maturity and are prepared, as far as size, color, etc., are con- 

 cerned, to become ordinary red corpuscles. It seems to me 

 that this fact is a very important one in its bearing upon the 

 question under discussion, and, so far as I know, it has not 

 been noticed before. I have been impressed with this pecu- 



