506 Caroline McGill. 



For demonstrating the gross form of the muscle fiber, macerating 

 fluids were occasionally used. Those giving the best results were 30 

 per cent ethyl alcohol, 30 per cent methyl alcohol, 20 per cent nitric 

 acid and various strengths of potassium hydroxid solutions. They 

 of course served as poor fixatives of the cell protoplasm as well as 

 macerating solutions. 



Most of the material was embedded in paraftin and cut in sections 

 from three micra to ten micra thick. To bring out the general form 

 of the smooth muscle fiber the thicker sections were often most useful. 

 Some tissue was embedded in celluloid, but only for comparison. 

 Fresh material cut on a freezing microtome immediately after removal 

 from the body gave for some purposes quite favorable results. 



Fresh material unstained was found to show much of the finer 

 structure of the tissue; however, for the more detailed work stains 

 were indispensable. Fresh muscle stained intra vitam by methylene 

 blue or neutral red ga^-e good results in some respects. 



Fixed material sectioned and stained was used for most of the 

 work. For all general staining, as well as for the demonstration of 

 contraction waves and myofibrillse, Heidenhain's iron-hsematoxylin 

 with a counter-stain of eosin or Congo red was found to give excellent 

 results. With this method, by staining and decolorizing for various 

 lengths of time, very different effects may bo produced. Moreover, 

 structures which are not shown by the ordinary method may be demon- 

 strated by repeated immersion in the hsematoxylin, followed in each 

 case by the extraction of the hsematoxylin in iron-alum. Iron- 

 hsematoxylin was especially valuable for staining areas of contraction 

 and for tracing the myofibrillse through such areas. When the 

 hsematoxylin is only partially extracted by the iron-alum the contrac- 

 tion waves are stained uniformly black throughout. Further extrac- 

 tion brings out the continuity of the myofibrillse through such areas. 

 ^Vhen the sections are further decolorized the hsematoxylin is entirely 

 removed from the contraction nodes before it leaves the nuclei. Such 

 sections counterstained in either eosin or Congo red show the contrac- 

 tion waves intensely red. 



Delafield's hsematoxylin, Hansen's hsematoxylin, and Flemming's 

 triple stain were also used as general stains. 



