244 THE RED BLOOD CORPUSCLES. [CH. X. 



with the depth of layer examined, as well as with the concentration of the pig- 

 ment. For accurate work the haematoscope should be employed. This is a 

 vessel with parallel glass slides i cm. apart. 



In handling the instrument the screw F is very liable to be turned, and 

 so the position of the scale to be shifted. From time to time, therefore, the 

 slit should be narrowed, and an observation made to ascertain whether any 

 shifting of the scale in reference to the D line has occurred. 



Record the absorption of light of the various pigment solutions on the 

 blank scale, to be found on page 372. Fill in with black pencil marks the exact 

 parts of the spectrum where light is absorbed, leaving the remainder blank. 

 It will not be found advisable to use coloured pencils. 



290. Oxyhaemoglobin. Take 5 cc. of distilled water in a test- 

 tube, and add one drop of defibrinated blood, shake well and 

 observe the spectrum of dilute oxy haemoglobin. There are two 

 absorption bands in the green. The one near the D line (the a band) 

 is somewhat narrower and darker than the ft band. The middle of 

 a is about X 578, and that of ft about X 540. 



291. Add two more drops of defibrinated blood and examine 

 again. The spectrum has become very much cut off, especially at 

 the blue end : the absorption bands have probably merged into one, 

 leaving a little patch of blue light and a broader belt of red light on 

 the two sides. If this effect has not been produced, add a little 

 more blood or dilute with water. Record the spectrum of the 

 solution on the chart as that of a medium solution of oxyhaemo- 

 globin. 



292. Add another drop or two of defibrinated blood, and note 

 that the blue light becomes absorbed, light only coming through in 

 the red. (Strong solution.) If the concentration is still further 

 increased, the red also is absorbed. 



NOTE. It is important to observe that a medium solution of oxyhaemo- 

 globin has a single band in the green. 



293. Haemoglobin (reduced haemoglobin). Treat 5 cc. of 

 water with one drop of defibrinated blood and thus obtain a solution 

 of oxyhaemoglobin of such a strength that two well-marked absorp- 

 tion bands can be observed. Add two drops of a solution of am- 

 monium sulphide, mix and warm to about 50 C., avoiding any 

 unnecessary shaking : or if Stokes' fluid is obtainable, add two or 

 three drops, in which case there is no necessity to warm. Note, in 



