202 THE AMERICAN" MONTHLY July] 



power for which the instrument has been made and the possi- 

 bilities by between 50 and 250 diameter magnification. To 

 find the actual field, measure the diameter of the field in mill- 

 meters and divide this by the previously ascertained magnifi- 

 cation. The diameter of the actual field will be the exact dis- 

 tance between the lines of the spiral groove. In most instru- 

 ments, 100 to 150 diameters give fields of 1 millimeter diameter, 

 just wide enough for the grooves, while the powers beyond these 

 furnish too small a space. It should therefore be exactly fitted 

 for one of the lower powers on the nose-piece of the microscope. 

 C, the table, is firmly but not permanently attached to the stage 

 of the microscope by means of pins and sockets, clamps, or 

 screws according to the stage of the instrument. 



In summing up, therefore, it is claimed, that this instrument 

 brings every portion of the slide ia succession and by the short- 

 est route into the focus of the microscope ; second, that it ad- 

 mits of more definite estimates of the contents of a slide ; and 

 third, that any object on the slide may be easily and definitely 

 recorded and found again with very little trouble. A patent 

 has been applied for. 



Two New Blood Stains. 



By W. DRESCHER, 



ROCHESTER, N. Y. 



Microscopists and Clinicians have for some time felt the need 

 of some method for the fixing and differential staining of the 

 various formed elements of the blood. Many attempts have been 

 made to answer this need, many methods have been suggested, 

 none seeming, however, to combine so maliy of the essential 

 qualities of a " good stain " as the method suggested and per- 

 fected by Dr. Ehrlich of Berlin. 



We should add to our list of re-agents two of the blood-coloring 

 solutions, now very generally used in EurO])e. In doing so, we 

 aid in bringing them into more general use, particularly in the 

 laboratories and hospitals of this country. 



The stains are, — (l)Ehrlich's Neutrophile Stain, (2')Chenzin- 

 skie's Eosin Methylene Blue Solution. The formuke for which 

 are as follows : 



