56 PRACTICAL PHYSIOLOGY. [vil. 



flint-glass prism in the centre of the apparatus. In C is fixed 

 a scale photographed on glass and illuminated by a fan- tailed 

 burner. D is the hsematinometer containing the dilute blood. 



(6.) Throw a piece of black velvet over the prism; light both 

 lamps; look through A; adjust the slit in B, and the telescope 

 in A, so as to get a good view of the spectrum, and over it the 

 image of the scale. D is supposed not to be in position at first. 

 On platinum wire, burn common salt in the flame to get the yellow 

 sodium line .D. Adjust the scale so that this line corresponds to 

 the figures 58.9 on the scale, and fix the spectroscope tubes (A 

 and C) in this position ; the scale is now accurately adjusted for all 

 other parts of the spectrum. 



" The numbers on the scale indicate wave-lengths expressed in 

 one hundred thousandths of a millimetre, and each division indi- 

 cates a difference in wave-length equal to one hundred thousandth 

 of a millimetre " (Gamgee.) 



Thus, Fraunhofer's line, D, which corresponds to division 58.9 

 of the scale, has a wave-length of 589 millionths of a millimetre. 

 The wave-lengths of Fraunhofer's lines are : A = 760.4, B = 687.4, 

 C = 656.7, D = 589.4, E = 527.3, F = 486.5. 



(c.) Using one of the blank maps supplied with Zeiss's spectro- 

 scope the maps correspond to the scale seen in the spectroscope 

 fill in, in wave-lengths, the position of Frauuhofer's lines B to F. 



(d.) Use a dilute solution of blood or haemoglobin i part in 

 1000 of water is best and place it in the hsematinometer, D, 

 which is placed in position between the flame and the spectroscope, 

 as shown in fig. 31. The distance between the parallel faces of D 

 is i cm. The spectrum shows the two absorption-bands of oxy- 

 hsemoglobin between D and E. The narrower, sharper, and blacker 

 band near D has its centre corresponding with the W.L. 579, and 

 it may conveniently be expressed by the letter a of the oxy 

 haemoglobin spectrum. 



The other absorption-band near E, and conveniently designated 

 /?, is broader, not so dark, and has less sharply defined edges than 

 a. Its centre corresponds to the W.L. 543.8. Notice that the 

 other parts of the spectrum are seen, there being only slight 

 cutting off of the red, and a slightly greater absorption of the violet 

 end. 



(e.) Work with a stronger solution of blood, and observe how 

 the two bands become fused into one, while more and more of the 

 red and violet ends of the spectrum are absorbed as the solution is 

 made stronger, until finally only a little red light is transmitted. 



2. W.L. of Absorption-Band of Reduced Hb. 



(a.) Adjust the apparatus as before, but reduce the oxy-hsemo- 



