25 



of lime, and the pith is devoid of such crystals. These observa- 

 tions are published more fully in the Monthly Microscopical Journal, 

 Dec. 1874. 



December 2, 1874. 



Measurements of Blood Corpuscles of Man, and of the Strice of 

 Pleurosigma. — Colonel Horsley showed and described the -working 

 of a microroetcr eye-piece, which had been made for him by Messrs. 

 Baker. Each of the divisions, with an object-glass of one-eighth of an 

 inch focal length, being equal to l-4000th of an English inch, and to 

 l-1200th of an inch with an objective of half an inch focus. To 

 show how readily very minute objects can be measured with this 

 instrument, red blood-corpuscles from the finger of one of the 

 members were found to have an average diameter of 1 -3200th of an 

 inch ; the striae of Pleurosigma formosum 1 -24,000th, and of 

 of Pleurosigma angiilatum 1-40, 000th; and these measurements 

 were as easily read off as those of lai'ger objects by a foot-rule. 

 The measurement of the red-corpuscles of human blood agrees with 

 that given in Mr. Gulliver's well-known Tables, appended to the 

 Sydenham Society's edition of the Works of William Hewson, 



r.R.s. 



