mollgaard's reticulum 325 



are brought into a 1.5 per cent aqueous solution of silver nitrate, 

 kept at a temperature of about 37°C. for three to seven days, if 

 unfrozen, and for one to three weeks if frozen, after which time 

 they are treated with a solution of pyrogallic acid, 2 grams, for- 

 mol 5 cc, and distilled water 100 cc, for twenty-four hours. 

 The smears are then placed in a 1 per cent aqueous solution of 

 gold chloride for five to ten minutes, brought into a 5 per cent 

 aqueous solution of sodium hyposulphite for ten minutes, carried 

 through distilled water and a series of alcohols of increasing 

 strength to xylol and mounted in damar or Canada-balsam. 



In the case of the neural tissue, the foregoing methods were 

 used almost exclusively. Variations were made only occasion- 

 ally and in fact so rarely that they need not be mentioned, ex- 

 cepting that some of the smears were stained for Nissl's bodies 

 without any previous fixation, and that in staining for neuro- 

 fibrillae a few control preparations were made according to 

 Legendre's ('06) modification of Bielschowsky's method. 



For control purposes too, smear preparations of hepatic and 

 pancreatic tissues were subjected to the above technique, and the 

 freezing of distilled water and egg-albumen was carefully studied 

 under various experimental conditions. 



It is thought unnecessary to describe the various magnifica- 

 tions employed in the study of the smears. An ordinary Leitz 

 oil immersion lens was in all cases quite sufficient to determine 

 the points in question. 



OBSERVATIONS 



The observations made may be conveniently assembled under 

 the following headings: 



Nissl's bodies 



1. In unfrozen smears 



2. In frozen smears 



a. Fresh, frozen, unfixed, and unstained smears 



b. Frozen, fixed, and stained smears considered as a whole 



c. Nerve cells of smears frozen at —5° to — 10°C. 



d. Nerve cells of smears frozen at — 10°C. and lower 

 Additional observations 



