THE AMERICAN 



MONTHLY 



MICROSCOPICAL JOURNAL 



YoL. YII. 



Washington, D. C, July, 1886. 



No. 7. 



Actinic Conti'ast in Photo-Microg- 

 raphy. 



BY GEORGE A. PIERSOL. M. D. 



The lack of appreciation of the in- 

 herent and unsurmountable limita- 

 tions of photo-micrography, as well as 

 failnre to secure those conditions most 

 favorable for satisfactory results, so 

 continually leads to disappointment 

 and condemnation that a repetition of 

 the essential conditions for such w^ork 

 may be pardoned. What is here 

 suggested is the teaching of no in- 

 considerable experience, embracing 

 almost every class of work with di- 

 rect sunlight from the heliostat. 



In this connection a brief word re- 

 garding the relative merits of lamp 

 and sunlight may, perhaps, be not 

 amiss. It will be admitted by every 

 one having had extended opportuni- 

 ties for comparison that sunlight, 

 properly handled, is the illumination, 

 par excellence, for all powers and for 

 all kinds of work. On the other 

 hand, however, with suitably arranged 

 lamplight, excellent work can un- 

 doubtedly be accomplished with low 

 and medium powers. Where high 

 amplifications are necessary (from 

 Soo to 2000 diameters) sunlight is so 

 immeasurably superior to lamplight 

 that all having occasion to use the 

 higher powers should give it a trial. 

 This can be done vs'ith an ordinary 

 mirror by simple and easily arranged 

 adjustments, although a heliostat is 

 desirable where much work is to be 

 undertaken. While photographs un- 

 der high powers are possible with 

 lamplight, we have yet to see a neg- 

 ative under looo diameters by lamp- 

 light which was comparable to that 



producible by properly managed sun- 

 'ight. 



Successful photo-micrography de- 

 pends especially upon these condi- 

 tions : — a. having all parts of the object 

 accurateh' in the same plane ; d. 

 having a well-marked differentiation 

 between the elements of the tissues ; 

 c. having the object so stained and 

 illuminated as to insure sufficient 

 actinic contrast between it and the 

 surrounding field or background. 

 The first condition is so evident that 

 it would seem entirely unnecessary 

 to more than mention it, and yet the 

 fact is continually forced upon us that 

 there is an insufficient appreciation 

 of the imperative necessity of having 

 this condition fulfilled to the greatest 

 possible degree. Only those having 

 had experience in photographing 

 delicate objects under high powers 

 .will realize the care requisite in the 

 selection of fields to secure all parts 

 in the same focal plane. 



Our modern histological methods 

 have given us the means, fortunately, 

 of providing sections whose thickness 

 embraces little more than a single 

 layer of cells. Sliding mici^otomes 

 and paraffin methods leave little to 

 be /ilesired on the score of sections. 



The second condition — difl'erentia- 

 tion of elements — is also obtained 

 with facility. For histological tissues 

 good hEematoxylin and carmine stain- 

 ings answer admirably. For very 

 thin sections deep carmine colorings, 

 with marked difierentiation between 

 cells and intercellular elements, are 

 probably to be preferred. 



The successful acquisition of the 

 condition of actinic contrast, however, 



