4 8 



PRACTICAL PHYSIOLOGY. 



[VI. 



veniently designated by the letter /?, nearer the violet end, is 

 broader and fainter. At the violet end the spectrum is shortened 

 by absorption (fig. 24, 2). 



(e.) Continue to dilute the solution, and note that the band near 

 the violet end is the first to disappear. 



. Using coloured chalks or pencils, sketch the appearances seen with 

 each dilution, and indicate opposite each the degree of the latter. 



(/.) A very instructive method is to make a pretty strong solu- 

 tion of blood, showing only one undivided band. Place a little 

 of this in a test-tube, and pour in water, so that the water mixes 

 but slightly with the upper strata of the blood. Examine the 

 solution spectroscopically, moving the tube so as to examine first 



B 



FIQ. 25. Graphic Representation of the 

 Absorption of Light in a Sptctrum 

 by Solutions of Reduced Hb, of dif- 

 ferent strengths. The shading indi- 

 cates the amount of absorption of the 

 spectrum, and the numbers at the 

 side the strength of the solution. 



CB 



FlG. 26. Graphic Representation of the 

 Absorption < f Light in a Spectm liy 

 Solutions of Oxy-haemoglobin, of differ- 

 ent strengths. The shading indicates 

 the amount of absorption of the spec- 

 trum, and the numbers at the side the 

 strength of the solution. 



the deeper strata of fluid until the surface is reached. At first 

 a single band is seen ; but as the solution is more dilute above, 

 the two bands begin to appear, and as the solution gets weaker above, 

 the /3-band disappears, until, finally, with a very weak solution, 

 such as is obtained in the upper strata only, the a-band alone is 

 visible. 



Fig 26 shows the amount of light absorbed by solutions of oxy- 

 haemoglobin (i cm. in thickness) and of various strengths. 



7. II. HsBmoglobin. 



(a.) To a solution of oxy-haemoglobin showing two well-defined 

 absorption-bands, add a few drops of ammonium sulphide, and 

 warm gently, when the solution becomes purplish or claret-coloured. 



(b.) Study the spectrum, and note that the two absorption- 



