94 THE AMERICAN MONTHLY [Mar., 



MICROSCOPICAL SOCIETIES. 



San Francisco, Cal., Geo. Otis Mitchell, Sec'y. 



March 7, 1894.— Mr. K. H. Freund spoke upon Paul Ehrlich's 

 method of staining the cell elements of the blood. He gave a 

 brief and interesting resume of our knowledge of the blood 

 from the time when Athanasius Kircher with his simple lens, 

 magnifying thirty-two diameters, observed and mistook blood 

 and pus corpuscles for worms. Later, in 1658, Swammerdam 

 observed the corpuscles in the blood of the frog, and in 1661 the 

 great Leeuwenhoek reported to the Royal Society his discovery 

 of the red corpuscles in the blood of man. Ever since then in- 

 vestigations into the nature and constituents of blood have held 

 the attention of numerous and enthusiastic workers. Apart 

 from mere histological interest it is evident that many questions 

 involving life and health can be answered only after a closer 

 knowledge of the obscure phenomena manifested in this vital 

 fluid, and their significance. As Goethe said, '' Blood is a very 

 peculiar juice." Chemistry has done its share in increasing our 

 knowledge of the subject, but the greater part of the work lies 

 within the province of the microscope. Rapidly enumerating 

 those whose investigations have thrown the most light upon the 

 subject, the author came to the new^ era inaugurated by Dr. 

 Ehrlich in 1880, when he announced his investigations as to the 

 " granular cell" by means of what he called his " tinctorial or 

 color analysis." This method is based upon the micro-chem- 

 ical behavior of the granulations of the protoplasm in certain 

 groups of leucocytes, or white blood corpuscles, toward a num- 

 ber of analine colors, and these effects are so constant and so 

 marked that his method has become an indispensable factor in 

 the clinical examination of the blood. Not only have Ehrlich's 

 researches into the nature of the granules occurring in the leu- 

 cocytes become means of the greatest histological and eventual 

 pathological value, but have also furnished the way to ascertain 

 the general condition of the blood and to obtain an exquisite 

 picture of its cellular elements. The granules in the leucocytes 

 present remarkable differences in their staining properties, dif- 

 ferences which have both a physiological and pathological sig- 

 nificance. Upon this basis he distinguishes five varieties of 

 what he calls " granules," designating them by the first five let- 



