468 SUMMARY OF CURRENT RESEARCHES RELATING TO 



plasm constitutes a physical system characterized above all by its 

 response to finely particulate matter. In the case of particles of ordinary 

 microscopic dimensions, this response (phagocytosis) is a behaviour 

 shared equally with the polymorphonuclear elements of the blood. But 

 towards the very much finer ultra-microscopic particles, the macrophages 

 react in a practically specific way, " drinking " them in, as it were, and 

 storing them either as free coagula in their protoplasm, or as the in- 

 habitants of watery vacuoles, where they oscillate in ceaseless Brownian 

 movement. They are able to store substances of importance to the 

 organism, and their action in this capacity appears to obey the principle 

 of a physiological balance. Only in cases where the local or general 

 content in the substance is very high do they load with it, and they 

 liberate their content in an impoverished fluid. In all processes con- 

 nected with tissue destruction the macrophages house the complex 

 chemical bodies set free, and so become the great cells finally so evident 

 to the eye. 



Mechanism of Mitosis.* — Marcus Hartog replies to criticisms which 

 Baltzer and Meek have brought against his theory of mitosis. His 

 general position is thus summarized. The processes, dynamic and other, 

 of the normally dividing cell may be analyzed as follows : 1. Such as 

 are known in the inorganic world : (a) osmosis and turgor, found in the 

 enlargement of the spindle ; (b) traction and tension of the viscid 

 threads of the spindle ; (c) fluid resistance deforming the " disceding " 

 chromosomes ; (d) solution and " desolution " ; (e) surface tension ; and 

 (/) electric phenomena. 



2. Such as are known to occur elsewhere in living plasma, but which 

 have not been adequately referred to physico-chemical phenomena : 

 (a) growth of chromatin substance and of chromatin fibres ; (b) proto- 

 plasmic movement, and especially that which is expressed in the elonga- 

 tion of the spindle ; (c) the transverse division of the elongated viscid 

 bodies with increase of their surface, occurring in the chromatin 

 granules at right angles to the chromosomes in which they lie, and in 

 the final division of the cell ; (d) the fusion and apparent loss of 

 identity of the daughter-chromosomes, and the reconstitution of the 

 daughter-nuclei. 



3. Mitokinetism, a force analogous to electrostatic force, manifested 

 in the karyokinetic field, in the splitting of the chromosomes, and in the 

 " discession " of their daughter-segments. 



4. Such as are found to have no clear equivalent elsewhere : the 

 resolution of the nuclear network into a definite number of chromo- 

 somes, the orderly sequence of events, the different phenomena leading 

 up by different roads to the same end. The process is incompatible 

 with reference to any single dominating force such as osmosis (Leduc), 

 or changes in electrostatic potential due to colloids (Lillie, Mann, 

 Gallardo). The author's answer to criticisms carries further his exposi- 

 tion of the fundamental physical and geometrical considerations on 

 which the mitokinetism explanation rests. 



* Arch. Bntwickl., xl. (1914) pp. 33-64 (16 figs.). 



