Chap, xxvi.] THE SPECTRA OF HEMOGLOBIN. 329 



positions of the dark lines of the solar spectrum ; and 

 the numbers indicate the wave lengths in millionth s 

 of a millimetre. 



The importance of these absorption bands of blood 

 is apparent. Even as the spectroscope supplies an 

 unrivalled means for detecting the presence of various 

 substances, so can it be made available for detecting 

 the presence of blood. In medico-legal inquiries, 

 therefore, it is of great value. A small quantity of 

 blood in an ordinary spectroscope will give the two 

 bands. They persist even after great dilution. If 

 the dilution be continued they begin to disappear, 

 first the band near the E line, and later that near the 

 D line. The adaptation of a spectral apparatus to the 

 ordinary microscope renders it easy to detect even a 

 very small trace of blood in a solution. 



The micro-spectroscope is the term applied to 

 the combined apparatus. A detailed description of 

 its const ru ction and method 

 of employment may be valu- 

 able. Browning, Hartnach, 

 and Zeiss all make the in- 

 strument. A sketch plan of 

 Browning's form is shown in 

 Fig. 152. It is made for 

 fitting into the draw-tube of 

 any ordinary microscope by 

 means of the tube M, the 

 eye-piece of the microscope 

 being removed. The con- 

 tinuation upwards of M is a 



wider tube, towards the upper F i g . i52.-The Micro-si 

 end of which there is a troscope. 



diaphragm E, with a slit, 



the diameter of the slit being variable by means 

 of a screw H. The light which has passed up the 

 tube of the microscope is thrown on the slit by 



Li^^^-vJJ 



ec- 



