mollgaard's reticulum 343 



in the size of the ice crystal, or crystals. This process of abstrac- 

 tion of water and enlargement of ice crystals continues until the 

 force of crystallization is equal to the force of imbibition, or 

 molecular capillarity, of the tissue element or cell, that is, until 

 an equilibrium is reached. With a new reduction in temperature 

 the process is again set up until the equilibrium is once more 

 restored. 



Whatever the exact details of the process may be, it is evident 

 that with the first formation of the center of ice crystallization 

 the tissue elements, and cellular elements especially, are sub- 

 jected to a displacement which is increased in extent both by 

 the expansive force of the water changing to ice and the actual 

 increase in size of the ice crystals under the force of crystalli- 

 zation. With a moderate rate of freezing (such as making smears 

 on shdes cooled to -20° to -40°C., with fixation at the same 

 temperature) and a like temperature reduction this displacement 

 gives rise to the various networks or sponge-like reticula described 

 for the egg-albumen, nerve cell, and so forth. These reticula 

 are therefore the resultant of aqueous abstraction, and displace- 

 ment of the subsequent tissue or cellular residue, as it were, by 

 the formation and growth of ice crystals or ice masses within 

 the tissue or cell. The expansion and contraction of the ice, 

 as the maximum and minimum temperatures for these phenomena 

 are reached and surpassed, augment the displacement, while the 

 force of imbibition is probably the main retarding force. With 

 very rapid freezing at very low temperatures ( — 50°C. and below) 

 the formation of multiple centers of crystallization subjects the 

 individual cellular elements to the contraction of the frozen mass 

 of course much more than at higher temperatures. That the 

 networks discussed arise in consequence of the displacement by 

 the enlarging ice masses is particularly emphasized by Miiller- 

 Thurgau, Molisch and Wiegand, as before stated. 



The blue and pink staining properties of the reticulum are 

 explained as being due to the fact that some of the substances 

 composing it are basophilic while others are acidophilic, that is, 

 some of the composing substance stains with toluidin-blue while 

 other portions of it stain with erythrosin. If now, we regard 



