METHODS OF INVESTIGATING ORGANIC MUSCLE. 201 



to four minutes in 4 cub. centim. of a solution of acetic acid, con- 

 taining from 0*5 to 1 per cent., and then for half an hour or more 

 in 4 cub. centim. of a O'Ol per cent, of chromic acid. Besides this 

 combined action of acetic and chromic acids, I can also recom- 

 mend acetic acid and alcohol both for the investigation of gold 

 preparations and of sections treated with solutions of gold 

 and chromic acid. The best materials are the urinary bladder 

 and the smaller arteries of the frog. For treating the sections, 

 carmine, anilin, chloride of palladium (F. E. Schulze), and picric 

 acid (Schwarz) may be employed. 



