1790 Journal of Applied Microscopy 



ment actuated by the vertical metal focusing rod. It is best to focus first on the 

 ground glass of the camera back and then to substitute for this the plain glass 

 and do the final focusing by means of the focusing lens. It sometimes happens, 

 especially with young embryos, that the object has no pronounced color differ- 

 ences or salient topographical features upon which to focus. Focusing is then 

 a matter of great uncertainty and many plates are spoiled. To overcome this 

 the following device has been used: A fine black hair from a sable brush is 

 clamped into the split end of a lead wire supported from a base ( Fig. 4) as in the 

 case of the reflector. By bending the wire the hair is brought against the object 

 to be photographed at about the point where it should be most sharply focused. 

 The hair is then focused, removed, and the exposure made. This procedure 

 saves much time. 



In making the exposure a shutter is used which consists of a disc of hard 

 rubber pivoted to a half ring of spring brass lined with chamois skin. The ring 

 slips over the lower end of the microscope tube. This is swung to one side for 

 the exposure by means of a little handle-like projection of the disc which extends 

 beyond the pivot and is swung into place beneath the microscope tube at the end 

 of the exposure (Fig. 4). 



If a flat opaque object, such as a chick blastoderm, is to be photographed it is 

 desirable to have it lie as nearly as possible in the focal plane of the objective. 

 To accomplish this the following device has been used (Figs. 4 and 4a): To 

 the center of a brass plate of the size and form of the microscope stage is sol- 

 dered a flat brass ring 40 mm. in diameter and 9 or 10 mm. high. There is thus 

 formed a shallow pan in the center of the brass plate. To the center of one face 

 of a small brass disc 80 mm. in diameter is attached by a stem '2 mm. long a 

 brass ball of about 6 mm. diameter. This ball is received into a socket between 

 the lower face of the brass pan and a small brass disc screwed to it, and this 

 socket is packed with oiled leather. The small metal plate then forms a sort of 

 false adjustable bottom within the pan. This pan is filled with alcohol placed 

 on the microscope stage, the specimen is laid on the false bottom and the bottom 

 then tilted until the specimen lies as nearly as possible in the focal plane of the 

 objective. The brass plate may be provided with holes, by means of which it 

 may be attached by pins inserted into the clip-holes of the microscope stage. 



The apparatus may be used with the microscope for transparent as well as 

 for opaque objects, whenever it is necessary to photograph such objects in a 

 horizontal position. It is merely necessary to leave the mirror and condenser 

 of the microscope in place and throw the light from the arc lamp onto the mirror, 

 from which it is reflected upward through the object. 



In photographing vertebrate embr}'0S as opaque objects I have found it of 

 the greatest advantage to use iion-halation plates. The plates render the texture 

 and surface relief of light colored or white objects with a delicacy and truthful- 

 ness that we have been unable to approach by any other means (Figs. 5 and (5). 

 The accompanying illustrations (Figs. 5 and G) are made with these plates. If 

 the object to be photographed necessitates the use of ortho-chromatic plates and 

 a color screen, the screen may be placed in front of the illuminating apparatus 

 or it may be placed inside the camera above the light excluding sleeve. 

 University of Michigan. JACOB Rekihard. 



