76 



SUMMARY OF CURRENT RESEARCHES RELATING TO 



until finally it reaches the paraffin. "When the last stop is is reached, 

 a special contact is made, which causes the catches a\ a\ to be released. 

 The counterpoises g g then descend along their guides, and the whole 

 inner casing, with its ring of copper vessels, is raised out of the thermostat. 

 This position is shown in fig. 114. In this position the paraffin cools and 

 solidifies. The block is now ready for the microtome. 



Fig. 113. 



Preparation and Staining of Neuroglia.* — H. von Fieandt employs 

 the following method. Small portions of tissue, not larger than 2 c.inm., 

 are taken from the fresh brain and fixed in Heidenhain's sublimate tri- 

 chloracetic fluid for 24 hours. They are then treated in 96 p.c. alcohol 

 for a week, and in absolute alcohol for two days, the alcohols being 

 changed twice a day. The material is now placed in cedar-wood oil for 

 24 hours, and then, after a further 24 hours in ligroin, is transferred 

 to a ligrom-paraffin mixture, and finally imbedded in paraffin (melting- 

 point 52°C). After cutting, the sections are fixed to the slide by the 

 Japanese method, freed from paraffin, washed in alcohol, and then treated 

 for an hour with alcoholic iodine. The preparations are then freed from 

 iodine with sodium tlliosulphate, washed in distilled water and stained 



* Arch. Mikr. Anat. u. Ent., lxxvi. (1910) pp/137-41. 



