122 



THE AMERICAN MONTHLY. 



[Jniy, 



is not always so readily had. While 

 the blue stainings (hEematoxylin, 

 meth^-l-blue) are, of course, more 

 actinically powerful than the reds 

 and browns, yet so much depends 

 upon the individual specimen in re- 

 gard to opacity and thickness that 

 each case must be determined for 

 itself. While a thick section stained 

 in carmine will yield but a dark mass 

 without detail, a similar section stained 

 in hiEmatoxylin may furnish a satis- 

 factory picture. But the days of thick 

 sections are passed ; the question now 

 is, how shall we stain and illuminate 

 the thinnest possible sections so as to 

 yield good photographs ? 



While a very delicate section well 

 stained with htematoxylin is all that 

 can be desired for examination, we 

 will soon find that actinically it is 

 far too transparent to produce a \ig- 

 orous photograph, there being insuf- 

 ficient actinic contrast between the 

 general blue color of the field illumi- 

 nated by the blue monochromatic 

 light from the ammonia-sulphate of 

 copper cell and the bluish purple of 

 the section. 



When the preparation of the speci- 

 men is under control, we believe it 

 will be found advantageous to pre- 

 pare a few sections as already sug- 

 gested in these columns,* by v^'hich 

 the thinnest sections in the brown 

 colors always markedly impress the 

 plate. 



In many cases, however, it is inex- 

 pedient to especially prepare objects 

 for photography. For such cases a 

 very valuable adjunct will be found in 

 the use of difterent colored lights pro- 

 duced by tinted glasses, carei^illy 

 adapted to the intensity and color of 

 the staining. The use of glass, or of 

 solutions of a color complementary 

 to that of the object, has been long em- 

 ployed in the arts in reproducing 

 paintings. Koch, in his ' Trau- 

 matic Infective Diseases,' relates his 

 experiences with this method, but 

 condemns it as impracticable. On 



* Staining Tissues /or Photography, Xm^-c. Monthly 

 Micr. Journ., March, 1885. 



account of the length of exposure and 

 vibration ' the picture does not have 

 sharpness of outline sufficient to enable 

 it to be of use as a substitute for a 

 drawing, or, indeed, even as evidence 

 of what one sees.'* 



Notwithstanding the unfavorable 

 experience of this skillful investiga- 

 tor some subsequent results by this 

 method have been most encouraging. 

 Defrenne obtained excellent photo- 

 graphs of the Bacillus tuberculosis 

 by means of fuchsin staining and 

 green glass, and quite recently our 

 own experience with this same bac- 

 terium and stain has been very grati- 

 fying. Since then a number of mod- 

 ifications have been tried. As a re- 

 sult of these experiments the practi- 

 cal deductions have been reached 

 that when the staining and thick- 

 ness of the specimen are insufficient 

 to give the necessary actinic con- 

 trast with the color of the field, 

 we can best succeed by employ- 

 ing a colored glass, whose tint will 

 be such as to give the contrast as well 

 as to aftbrd light to sufficiently im- 

 press the plate where not occupied by 

 the object. Such a color will not be 

 the complementary one in many in- 

 stances. With blue stainings the use 

 of the complementary yellow would 

 yield but a faint image, since the weak 

 actinic power of the transmitted rays 

 are insufficient to deeply affect the 

 unoccupied parts of the field. The 

 substitution, however, of a suitable 

 shade of green affords sufficient con- 

 trast of the object as well as permits 

 the passage of rays sufficiently actin- 

 ically powerful to adequately impress 

 the surrounding parts of the plate. 



With all these colors the exposure 

 is greatly lengthened ; with a medium 

 green it being five to seven times 

 longer than with blue light ; as, how- 

 ever, the normal exposvire is seldom 

 over one second, the increase has 

 practically little disadvantage. Not 

 only for very minute objects, as bac- 

 teria, stained with methyl-blue, un- 

 der high power, but equally for very 



* Magnin-Sternberg. Bacteria; 2d ed., page 195. 



