A Standard Micrometer. 47 



ing them with solutions of corrosive sublimate — in some cases 

 bringing on death immediately, in others not until the lapse of 

 several days. The blood was examined both before and after 

 death, and no change was discerned in the appearance of the 

 blood-corpuscles, except in a few instances, when there was 

 noticed some change in their shape. This is not what one 

 would anticipate from a perusal of Prof. Boettcher's article. 



" However, by following the method given in the last number 

 of your journal, we have demonstrated this nucleus in the red 

 corpuscle of man (as previously reported), the dog, cat and rat. 

 The most satisfactory result was obtained from the blood of 

 the rat ; the most unsatisfactory from that of man. No value, 

 however, is attached to this fact. 



" By using higher powers than at first emplo5'ed, we are posi- 

 tive there is a granular appearance to this nucleus, not present 

 in other parts of the blood cell. In some cases this is quite 

 marked, especially when the nucleus is large ; and also in those 

 corpuscles where we have seen a nucleolus, this granular struct- 

 ure is very evident. This is what we should expect when ac- 

 cepting Beal's theory of protoplasmic matter. 



"In some specimens examined, the proportion of nucleated to 

 non-nucleated cells was very small indeed, while in other speci- 

 mens the proportion was much greater." 



A STANDARD MICROMETER.* 



BY R. HTTCHCOCK. 



The subject that I wish now to bring before this convention 

 is of such importance that it seems hardly necessary to say 

 anything to call your attention to it. 



The need of a definite and accurate standard for microscopic 

 measurement has been recognized by some for many years. 

 As an example of this, Prof. Lyons, in 1857, proposed to the 

 British Association for the Advancement of Science that "some 

 definite micrometric integer should be assumed, being a de- 

 terminate part of unity." He suggested as a name for this 

 integer, that it should be called a micro-line, and thought that 

 a good provisional standard would be the i-ioooo of an 

 English inch, but his preference was for a decimal scale. 



* Abstract of a paper read at the National Microscopical Congress, Indianapolis, Aug. i6, 1878. 



