and Laboratory Methods. 



228/ 



CYTOLOGY, EMBRYOLOGY, 



AND 



MICROSCOPICAL METHODS. 



AGNES M. CLAYPOLE, Throop Polytechnic Institute. 



Separates of Papers and Books on Animal Biology should be sent for Review to Agnes M. Claypole, 



55 S. Marengo Avenue, Pasadena, Cal. 



Ji 



Shaw, Philip E. Electric Method of Taking A small apparatus has been made by 

 Microscopic Measurements. Journ. Roy. modifying designs described two years 

 Micr. Soc, Pt. 6, 625-630, 1902. •' ° ^ , r.- ^ \^^ 



previously, called " The Simple Elec- 

 tric Micrometer," capable of giving measurements of y^Vo o^ "^"^- 0^ ^^^^- This 

 has two points in its favor — first, it is electric ; second, it is a direct method. 



In the diagram (Fig. 1) the essential parts are shown. The slide, s/, is 

 mounted on the stage s, o being the microscope objective. A screw, sc, is 

 brought up to nearly touch the edge of the stage. This screw is carried by a 

 nut, //, and has a graduated disc, d, with a milled head, m, attached to it. If 



Fig. 1. 



the screw should have two threads to a mm., and the graduated disc 500 divis- 

 sions, then a movement of the screw-disc by one division corresponds to a 

 movement of the screw-point, /, by .001 of a mm. or one micron. The micro- 

 meter-screw is supported on a stand quite separate from the microscope, so that 

 it can be packed separately. There is a universal joint, /, between the screw and 

 the stand, so that the screw can be raised, lowered or pointed in any desired 

 position and then clamped. Suppose the screw and stage to be brought into 



