MICROINCINERATION 141 



that motion pictures of incinerating sections of skeletal muscle and 

 of anterior horn cells at 700-800 X magnification reveal no distor- 

 tion, Scott (1943). The advantage of microincineration over chemi- 

 cal tests for the determination of the anatomical disposition of 

 mineral constituents lies in avoiding inevitable displacements and 

 losses resulting from the use of solutions. In addition, the danger 

 of fortuitous adsorption of reagents on colloidal protoplasmic sur- 

 faces is circumvented. The present limitations of the technique lie 

 in its essential morphological character, which leaves not only 

 quantitative but qualitative chemical considerations very largely 

 in the dark. Only a few elements can be detected in incinerated 

 preparations, and only a rough estimate of the quantity of ash in a 

 given location can be made. 



The microincineration technique was originally developed by 

 Policard and co-workers in France and was introduced in America 

 by Scott. The more recent refinements have resulted chiefly from 

 the careful and extensive researches of Scott and collaborators. 

 The earlier reviews by Policard (1931-1932) and Policard and 

 Okkels (1931) and the later ones by Scott ( 1933a,1937,1943) and 

 Gage (1938) thoroughly cover the development and applications 

 of this technique. 



Engstrom ( 1944) carried out a very nice study on the localization 

 of mineral salts in striated muscle fibers by employing ultraviolet 

 absorption followed by microincineration of the same section. By 

 correlation of both techniques he was able to conclude that the 

 intensely absorbing isotropic segments which contain the adenylic 

 acids yielded the ash, w^hereas practically no ash was derived from 

 the weakly absorbing anisotropic segments. 



1. Preparation for Incineration 



Some of the earlier work dealt with the use of various solutions 

 for the fixation of tissue in preparation for microincineration, and 

 it was found that absolute alcohol or an alcohol-formalin mixture 

 w^as best since their use resulted in a smaller loss of mineral matter 

 than was observed with other fixatives. In Scott's (1937) hands the 

 intracellular distribution of minerals was preserved remarkably 

 well when the tissue was fixed for 24 hr. in a solution of 9 vol. 

 absolute alcohol and 1 vol. neutral formalin followed by treatment 



