THE VITAL PHENOMENA OF THE CELL 207 



Flemming (VI. 13, 1891) and Hermann, by means of double 

 staining with safranin-haomatoxylin, safraiiin-mauvine, safranin- 

 gentian, etc , have obtained a similar alteration of staining re- 

 actions in animal cells, varying according to the condition of the 

 nucleoli. "It appears to me important," says Flemming on this 

 occasion, "that in those stages when nucleoli are still present, or 

 have only just disappeared, or have just reappeared, the chromatin 

 figure inclines towards a blue coloration, whereas in those cases 

 where the nucleoli are quite disintegrated the figures are distinctly 

 safranophil, just like the nucleoli." 



2. Direct Nuclear Division. (Direct nuclear multiplication, 

 fragmentation, amitosis, amitotic division.) 



As a contrast to the complicated processes connected with seg- 

 mentation, nuclear division may take place apparently in a very 

 simple manner. This is called fragmentation, or direct nuclear 

 division, and is seen in a few kinds of cells. Under these cir- 

 cumstances spindle threads, nuclear segments, and protoplasmic 

 radiations are not seen. The division of the nucleus appears 

 rather to proceed in a manner resembling that described by the 

 earlier histologists. It can be most easily observed in the lymph 

 corpuscles, both when alive, and when fixed by means of reagents. 



There are various ways in which good preparations may be 

 made : a drop of lymph may be drawn up from the dorsal lymph 

 sac of a. Frog into a fine capillary tube, and then placed upon a 

 slide and covered with a cover-glass, the edges of which should 

 be smeared with paraffin, in order to protect the preparation from 

 evaporation. Or a small glass chamber may be prepared accord- 

 ing to Ziegler's method, by fastening together by their four corners, 

 or by two of their sides, two extra thin cover-glasses, so that there 

 is a capillary space between them. The glass chamber is then 

 placed for one or more days in the dorsal lymph sac of a Frog, 

 during which time a large number of lymph cells make their way 

 between the two cover-glasses, where they undergo changes. The 

 third method, recommended by Arnold, is to place a thin pervious 

 disc of elder pith in the lymph sac. After a few hours numbers 

 of leucocytes have attached themselves to its sui-face, and are thus 

 available for observation. Later on, thin layers of fibrin, pro- 

 duced by coagulation, are deposited upon the disc of elder pith ; 

 these may be removed, and, with the cell elements which are 

 attached to them, may be easily examined. 



Ranvier (VI. 54) observed all the phenomena of division take 



