ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 



251 



be -removed to uncontarninated alcohol. Treatment of nervous tissues 

 with methylated spirits gives extremely bad results, and with unstriated 

 muscle also the results are most unsatisfactory. For hardening and 

 staining purposes, this reagent is quite as good as the ordinary 90 p.c. 

 alcohol. 



Preparing Delicate Embryonic Tissues for Histological Examina- 

 tion.* — For cytological and histogenetic investigations of Vertebrate 



Fig. 38. 



embryos/ A. Maximow has devised modified methods of fixation and 

 imbedding suitable for such easily damaged material. As fixing re-agent, 

 he uses a modified Zenker's fluid of the following composition : — For- 

 malin 10 c.cm., sodium sulphate 10 grrn., potassium bichromate 25 grm., 

 corrosive sublimate 50 grm., distilled water 1000 c.cm. For some pur- 

 poses he adds 10 c.cm. of 2 p.c. osmic acid to this solution. In the case 

 of larger embryos the specimen must be so prepared by incision, or other- 

 wise, that the fixing fluid can readily gain access to all parts. After 

 careful dehydration the specimens are imbedded in celloidin and cut by 



Zeitachr. wiss. Mikrosk., xxvi. (1909) pp. 177-90. 



S 2 



