mollgaard's reticulum 323 



neck obtained by the decapitation contains a portion of the 

 spinal cord varying from the first to the fifth cervical segments 

 according to the adjustment of the apparatus and as to the par- 

 ticular place on the neck where the blow happens to fall. This 

 neck segment should of course be obtained as soon as possible 

 after the blow is struck. Then, with or without depriving the 

 segment of its adherent musculature, a long slender knife is passed 

 around the spinal cord just within its dural sheath. Simultane- 

 ously, one of the assistants carefully grasps an end of the cord 

 and drawing it from the canal quickly hands it to the investi- 

 gator. The isolated cord segment is now cleft longitudinally in 

 the region of the anterior horns. From the exposed gray sub- 

 stance (anterior horns) smears are made on glass slides which 

 are dropped into Coplin jars containing the fixing fluids. When 

 the foregoing was carefully and successfully carried out it was 

 found that the smears could be placed in.the fixing fluids twenty- 

 five seconds after the moment of decapitation. 



Fixation was carried out both with and without freezing; that 

 is, in the one case the jar containing the fixing fluid was sur- 

 rounded by a freezing mixture while in the other case it was 

 not. In general, 96 per cent alcohol was used as a fixative for 

 Nissl's bodies; and, when the smears were frozen, for the neuro- 

 fibrillae also. For fixing the neurofibrillae of unfrozen smears 

 the fluid (24 parts absolute alcohol, and 1 part ammonia) recom- 

 mended by London ('05) was more frequently used. For com- 

 parison and checking of results on the Nissl's bodies, Ohlmacher's 

 fluid and formol-corrosive were used in a few cases. For a like 

 purpose 12 per cent formol was used as an additional fixative 

 for the neurofibrillae in a few instances. The length of time the 

 smear preparations were left in the fixatives varied in the case 

 of the Nissl's bodies from one-half hour to three days, and for 

 the neurofibrillae from five hours to four days. 



Fixation with freezing, to be more explicit, was carried out 

 as follows: A medium sized vessel (capacity approximately one 

 gallon) containing 95 per cent alcohol was placed within a larger 

 container. In the smaller vessel with the alcohol were placed 

 small Coplin jars containing 96 per cent alcohol and ten or twelve 



