There are two methods of studying the histologic structure of any tissue. One is by determining the morphology and specific staining affinities of the component cells in fixed sections. This method of attack has brought fruitful results in the classification of the gliomas.1 The other mode of approach, the direct observation of living cells, has not been used extensively in pathologic investigations, for the securing of cells of most human tissues in a viable condition is a matter of considerable technical difficulty. The methods which are at hand, the technics of supravital staining and of tissue culture, have had only a limited application. Whether or not these special procedures for the study of living cells will find an increasing sphere of usefulness in laboratories of pathology depends as much on the possibility of their adoption as a routine measure without a prohibitive amount of special training as on a