CHAP. II.] THE BLOOD. 99 



FIGURE 22. 



Spectrum 1. (Preyer, Plate 1, sp. 2 modified.} Solution of oxy-haemo- 

 globin containing less than O'Ol p. c. In this as in every other case, a 

 stratum 1 centimetre thick was examined. One distinct, though faint, 

 absorption band (a) between W. L. 583 and 575'1. According to Preyer 1 there 

 is no trace of the band ft seen ; the Author finds, however, that whenever a 

 is visible he perceives a faint shadow in the position of wave-lengths 538 

 550. There is no absorption at either violet or red end of the spectrum. 



Spectrum 2. (Preyer, PI. 1, sp. 4.) The solution contains 0'09 p. c. of 

 oxy-haemoglobin, a extends from 583 571 and ft from 550 532. The 

 violet end is absorbed to about 428. The red end is scarcely affected. 



Spectrum 3. (Preyer, PI. 1, sp. 6.) The solution contains 0-37 p. c. 

 of oxy-haemoglobin, a extends from 589 567, and ft from 553 523. 

 The red end of the spectrum is perceptibly shortened. The violet is entirely, 

 and the blue partly, absorbed, to about 453. 



/Spectrum 4. (Preyer, PI. 1, sp. 8.) The solution contains 0-8 p. c. of 

 oxy-haemoglobin. The two absorption bands have amalgamated and one 

 broad band is seen extending from 595 to 518. The green is just visible 

 between 518 and 498 ; the slightest increase in the strength of the solution 

 causes the green to disappear. 



Spectrum 5. (Preyer, PI. 1, sp. 9.) Solution of haemoglobin (Syn. 

 reduced haemoglobin) of about 0'2 p. c. A single broad band with diffuse 

 edges, between 595 and 538; the band is darkest at about 550. Both 

 ends of the spectrum are more absorbed than by a solution of oxy-haemo- 

 globin having the same degree of concentration. 



Spectrum 6. (Preyer, PJ. 1, sp. 14.) Solution of carbonic oxide hae- 

 moglobin. Two absorption bands very similar to those of oxy-haeino- 

 globin, but moved somewhat nearer to E. a extends from 587 to 564 and 

 ft from 547 to 529. The blue and violet are less strongly absorbed than 

 by a solution of oxy-haemoglobin of the same strength. 



On diluting very largely with water nearly the whole of the 

 spectrum appears beautifully clear except where the two absorption 

 bands are situated. If dilution be pursued far enough even these 

 disappear; before they disappear they look like faint shadows 

 obscuring the limited part of the spectrum which they occupy. The 

 last to disappear is the band a. 



The two absorption bands are seen most distinctly when a stratum 

 1 cm. thick of a solution containing 1 part of haemoglobin in 

 1000 is examined; they are still perceptible when the solution 

 contains only 1 part of haemoglobin in 10000 of water. 



Haemogio- The spectrum of oxy-haemoglobin had been de- 



scribed b J Hoppe-Seyler when Professor Stokes made 

 the remarkable discovery that when diluted blood is 

 treated with certain reducing agents the colour of the liquid and 

 its spectrum undergo remarkable changes ; the former loses its bright 

 red and acquires a brown colour, whilst the green interspace which 



1 Die Blutkrystalle : Untersuchungen von W. Preyer; mit drei farbigen Tafeln, 

 Jena, 1871. 



72 



