220 American Quarterly Microscopical Journal. 



Compared with space 2 at 68^, No. 12 is ,000019 cm. too long. 



Compared with space 8 at 61°, No. 12 is .000005 cm. too long. 



When the last degree of precision is required, the stops 

 should be set independently for each centimeter of the stand- 

 ard bar, with its proper correction applied, and the centimeter 

 whose value is desired should then be compared with the dis- 

 tance between the stops in each case. 



Finally, we have a severe test of the accuracy of the graduation 

 in the value of the centimeter in terms of the inch. The end 

 line of the centimeter falls between line 39 and line 40 of the 

 inch. The following measures give the distances from line 39 

 to the end line of the centimeter: 



Mean, .003707 

 The value of the centimeter in terms of the inch is 



I cm = .393707 inch. 

 The value generally given is 



•393708 



Since the value obtained involves the mechanical error of 

 making a coincidence between the first lines, this agreement 

 is rather more close than ought to be expected. 



Har\'^ard College Observatory. 



PRACTICAL HINTS ON PREPARING AND MOUNT- 

 ING ANIMAL TISSUES. 



BY CARL SEILER, M. D 



{^Continued.) 



STAINING. 



After the section has been cut anti placed in alcohol, it is 

 ready for staining with one of the many preparations recom- 

 mended in the books. It is not my intention to point out the 

 merits and demerits of the various staining processes, but I 



