rfRREN PIGMENT OF INTESTINAL WALL OF CH^TOPTERUS. 4G3 



examined as to light intensity, was on the average eqvial to 

 I'OOl iJL wave length. For example, for determining the 

 intensity at X = 600 /x^, the spectrum strip lying between 

 wave lengths 0597 fi and about 0*630 ix was isolated by means 

 of the ocular screw diaphragm slit (accordingly the rest of the 

 spectrum shut off). In the outermost red, where the disper- 

 sion is too small, spectrum strips of 0*01 — 0*02 breadtli were 

 isolated. 



The coloured solutions were examined in small glass chambers 

 of known height, which I had prepared for the purpose by 

 Zeiss. They are to be recommended also for merely qualita- 

 tive spectroscopic observations on coloured solutions, since one 

 can work with a very small quantity of fluid (a few cubic 

 millimetres). I intend soon to describe them and explain their 

 use more fully. You can get them from Zeiss. 



As you will observe, I have analysed a neutral as well as an 

 acid and alkaline solution. All three show characteristic 

 differences, and indeed the colours also appear different to the 

 eye. It is a pity that neither Bonellin nor Chsetopterin have 

 been prepared in a chemically pure state, and perhaps cannot 

 be. If they were, one could make exact determinations upon the 

 (clearly very great) influence of the solvent upon the concen- 

 tration of the solution. 



VOL. 40, PART 3. NEW 8ER. I I 



