mollgaard's reticulum 321 



is wholly an artefact. He, however, entertains the hope that 

 the method may still be utilized in studies dealing with physio- 

 logical and pathological changes in nerve tissue. 



From the foregoing it will be observed that it may still be 

 considered questionable : 



1. Whether the Nissl's bodies and neurofibrillae are present in 

 the freshly fixed nerve cell. 



2. Whether freezing the fresh neural tissue at a low tempera- 

 ture so changes the cytological structure that neither Nissl's 

 bodies nor neurofibrillae can be demonstrated. 



3. Whether the Nissl's bodies and neurofibrillae are due to 

 post-mortem changes. 



4. What the relation is of Mollgaard's reticulum to the Nissl's 

 substance. 



5. How and why Mollgaard's reticulum, or 'glia-network,' is 

 formed during the freezing. 



The observations made in the present study will afford at 

 least a partial answer to these questions. 



MATERIALS AND TECHNIQUE 



With one exception, the tissue studied was taken from the 

 spinal cord of the dog. The exception was that of a horse killed 

 by the Department of Veterinary Medicine of the University of 

 Missouri. In addition to neural tissue, several other tissues and 

 different fluid masses were used, but as these were employed 

 expressly for control observations they will be referred to only as 

 occasion demands. The number of dogs used was twenty-four. 

 They were obtained, as a rule, the day before they were to be 

 killed, from the city pound or from individual owners. Such 

 public source of course means that the dogs were of varied breed 

 and description. Care however was taken that only healthy, 

 well-nourished, active dogs were used. Likewise much care was 

 exercised in avoiding exciting or in any way injuring the animal 

 before it was killed. It was sought in general to use adult dogs 

 of medium size and of an age that did not lie below one year 



