and Laboratory Methods. 



1527 



Fig. 3. — Malignant (Edema, 2 mm. oil immersion, apochiomatic 

 objective, and a No. 4 projection eyepiece with camera e.\ten- 

 sion of 66 inches. The magnification is 3000 diameters. 



of our microscope stand are necessary, namely, the large tube, two inches in 

 diameter into which the objectives screw without collars, and the improved fine 

 adjustment which lowers or raises the objective only .04 of a millimeter for an 

 entire round. As it can easily be turned less than a degree, the distance from 

 the object to the objective can easily be varied .0001 mm. 



The camera is large enough 

 to carry a six and one-half by 

 eight and one-half plate and 

 can be extended six feet. 



The optical bench carries 

 the arc light and all the illumi- 

 nating accessories somewhat 

 as the camera is carried ; all 

 these are adjustable up and 

 down, to and from the light, 

 and from side to side. 



The necessary accessories 

 are a pair of condensers (//), 

 a cooling cell (/), two ray 

 filters (y), a field diaphragm 

 (/'), and a double convex lens 

 not shown in the cut, as the 

 instrument was arranged for low power work at the time the photograph was 

 made ; these are necessary, in the sense that one pays more in time and failures 

 for not having them than they cost. 



These tables, benches, condensers, and cells should all be carefully levelled ; 

 this is done by means of a spirit level and adjustable feet and clamps, one or the 

 other of which they all have. Our cooling cell is three and a half inches long 

 and four and a half inches in diameter ; we keep it filled with water and have 

 never had either a slide or an objective perceptibly warm, though we have kept 

 them exposed for hours together. The tradition that calls for alum in the cell is 

 not valuable. In a future article on " Illuminating the Object," the use of the 

 other accessories will be explained. It follows from what I have said, that a 

 laboratory costing some thousands of dollars is necessary for the best results in 

 photomicrography. Experience convinces me that it is equally necessary for an 

 expert microscopist and photographer to be in charge of it ; he then could do 

 all work of this sort in conjunction with all departments of a university, or pos- 

 sibly of more than one university. A joint laboratory used by a dozen different 

 men, all mainly interested in something else, will yield in the future results simi- 

 lar to what it has in the past. The discouragement one hears on every hand is 

 not well founded ; it is traceable to the notion that photomicrography is a simple 

 art that any one can practice. If courses of instruction were given in our leading 

 universities in connection with such laboratories, it would soon come to pass that 

 we should be as well off in photomicrographic manipulators as we are now in 

 microscopists. 



Recently, at the seaside laboratory of the Misses Foot and Strobell, I saw 

 some excellent work done with very simple apparatus; their work follows entirely 

 new lines ; in a future article on " Focusing the Instrument," I shall describe 

 their arrangement. 

 Earlham College. D. W. DenniS. 



