MUSCLE. 405 



18. For decalcification of bone, see above. 



19. Bones and teeth may be ground down to make dry 

 sections. A well -macerated and fat-free bone is cut into 

 sections 1-1 mm. thick. These are rubbed first on emery 

 paper and then on a glass plate with pumice on it. This can 

 be accomplished best with the end of the fingers. A drop of 

 water occasionally is added. When the section becomes very 

 thin, it is washed in water, and polished on both sides on a 

 hone and dried. It should be mounted in balsam which is so 

 thick that it will not enter the air spaces. 



20. In order to render the various canals and spaces of 

 bones and teeth more distinct, they must be filled with a colored 

 fluid. The best results are obtained in the following way : a 

 dried and fat-free bone or tooth which has been macerated is 

 cut into sections. These are boiled on a sand-bath for at least 

 an hour in a mixture of equal parts of saturated solution of acid 

 fuchsin and methyl-violet in absolute alcohol, until the remain- 

 ing fluid is thick. The sections are then dried for twenty- four 

 hours or longer in a thermostat (40 C.), and afterward ground 

 down and polished as described before, xylol being used, how- 

 ever, instead of water. 



4. MUSCLE. 



21. Muscle may be studied in the fresh condition, by teasing 

 out the fibrils in glycerin and staining with methylene-blue. 

 Acetic acid brings out the nuclei. 



22. The fibrils may be isolated by macerating the muscle 

 in 0.1 per cent, chromic acid, or 33 per cent, alcohol for twenty- 

 four hours. 



23. The muscle of Hydrophilus hardened for twenty-four 

 hours in 93 per cent, alcohol shows the fibrillar structure on 

 teasing. 



24. For the isolation of heart muscle, and smooth muscle 

 elements, potassium hydroxide (33 per cent.), is used. In order 

 to obtain permanent preparations of these elements Schieffer- 

 decker suggests allowing the hydroxide to act for twenty min- 

 utes, and then adding 50 per cent, acetic acid to neutralize the 



