100 PHYSIOLOGICAL CHEMISTRY. 



found in human gall stones, and in the dog is abundantly deposited 

 along the edges of the placenta. 



The spectrum of biliverdine is marked by a very distinct and dark 

 absorption band in the red, at the situation of the line C, extending 

 thence to the left toward the line B. Its width increases with the 

 thickness of the layer of fluid examined, and when this exceeds a cer- 

 tain limit the whole of the red disappears. The band rarely reaches 

 the situation of the line B, and seldom or never passes beyond it, with- 

 out extinguishing at the same time all the red light of the spectrum. 

 In layers of green bile, two or three centimetres in thickness, it is 

 quite dark, often almost black, while the red on each side of it is still 

 very brilliant. 



As a rule, the intensity of the absorption band at C is in proportion 

 to the preponderance of green in the color of the bile. Though easily 

 seen, in comparatively thin layers, in specimens of a pure green or 

 a decided greenish-olive color, it is less perceptible in those of a 

 yellowish, yellowish-brown, or olive-brown tint. But if a specimen 



FIG. 14. 



SPECTRUM OF GREEN (SHEEP'S) BILE. 



of reddish or yellowish-brown bile, which does not show the band 

 distinctly, be turned green by the addition of a few drops of an iodine 

 solution, the band at C at once becomes visible, often to a very marked 

 degree. It is, therefore, no doubt the characteristic absorption band 

 of biliverdine. (Fig. 14.) 



There are two other absorption bands in the spectrum of bile, less 

 constant and much less distinct than that at the line C. One of them, 

 very dim and ill-defined, is situated at the junction of the orange and 

 yellow, immediately to the left of the line D, occupying about the last 

 third of the space between C and D, The remaining band is much nar- 

 rower than either of the others, but somewhat more distinct than the 

 second. It is situated in the yellow, at about one-third the distance 

 between D and E. The last two bands are more frequently visible in 

 sheep's bile than in that of other animals ; but all three may be some- 

 times seen in a watery solution of desiccated ox-bile, which has been 

 kept, in the form of a dry powder, for several years. 



The spectrum of bile also exhibits a remarkable diminution in 

 intensity of the orange and yellow colors. The situation of the second 



