FORENSIC MICROSCOPY. 133 
lines, which are due to the presence of the cooling vapors 
of metallic elements in the surrounding atmosphere, each 
of which absorbs the light corresponding to its own 
bright line spectrum. The Frauenhofer lines may be con- 
sidered the shadows of the spectra of the metals in the 
outer atmosphere of the sun. 
Obviously artificial light should be used for the micro- 
spectroscope, since the Frauenhofer lines would intro- 
“duce a confusing element. When various solid and 
liquid substances are placed on the stage of the micro- 
scope, absorption spectra of the same general type as 
that of sunlight are produced, although the dark bands 
are wider and less sharply defined, this being more and 
more the case as the thickness of the body is increased. It 
is therefore desirable to examine layers of varying depth, 
and this may be done by means of a cell made by cement- 
ing to a slide a piece of heavy glass tubing cut off obliquely 
so that it shall be 5 mm. deep on one side and o.5 mm. 
deep on the other. 
The application of the microspectroscope to the exam- 
‘ination of various organic bodies has not yet been 
developed to anything like its possible limits. It has 
yielded interesting results in the study of certain animal 
and vegetable coloring-matters; but its chief use has 
so far been in the detection of blood-stains, since the 
red coloring-matter of blood produces characteristic 
spectra. Suspected blood-stains which are to be thus 
examined may be treated with distilled water until a 
reddish-brown solution is produced, when it is apparent 
that hemoglobin has gone into solution. The liquid 
