320 THOMAS J. HELDT 



holds the freezing method to be one of the poorest. Of this 

 fact he says he convinced himself in the year 1874, when he 

 carried out a large number of experiments in this connection, 

 some of which may be briefly mentioned. Under the microscope 

 he followed the very foiTaation of the network which Mollgaard 

 describes at such great length. He likewise examined the freez- 

 ing process in all its phases for a large series of tissues and fluids 

 (blood, glue, egg-albumen, starch-paste, etc.) and arrived at the 

 certain conviction that this 'vital' method is very treacherous 

 for scientific purposes and should be strongly condemned. From 

 his studies Retzius concludes that the network observed in the 

 frozen preparations is due to distortions and lacerations brought 

 about by a system of spaces, passages, lacunae, clefts, and tubules 

 filled with crystals of ice. He says that if to the frozen prep- 

 arations a fixing fluid (alcohol, osmic acid, etc.) is applied, the 

 system of clefts and lacunae, with the distortions and lacerations 

 incurred, is preserved in all detail; but, if on the contrary, the 

 preparations are permitted to thaw out without previous fixation, 

 the water reappears anew in the entire mass, and only here and 

 there a small cleft is left behind. From a consideration of the 

 entire phenomenon it is evident to him that the water contained 

 in the tissue or the fluid mass at the moment of the freezing 

 passes out of the parenchyma and collects itself in the passages 

 and lacunae which then appear in the frozen condition filled with 

 crystals of ice. The water apparently collects where it meets 

 with the least resistance. The foregoing results and others ar- 

 rived at by Retzius together with Key were published by them 

 in the Swedish language in 1874 and in the German language in 

 1882, so they should have been quite accessible to Mollgaard. 

 Retzius in brief affirms that Mollgaard's 'glia-network' is an 

 artefact due to the technique employed, but farther than this 

 he does not criticise Mollgaard's ideas and results. 



Mollgaard ('lib) in replying to Retzius' criticism, says that 

 he very much regrets that the articles by Retzius and Key so 

 long ago escaped his notice, for on duplicating some of their 

 experiments he is forced to acknowledge that his 'glia-network' 



