76 The Microscope. 



be changed, except the solution or fluid to be examined." The 

 oxidized blood bands are seen on the diagram No. 1. 



DEOXIDIZED OR VENOUS BLOOD. 



We have already adverted to the fact that blood may exist in a 

 double state of oxidation. When saturated vy^ith oxygen we call it 

 oxidized blood. It corresponds to the arterial blood in the living 

 body. It is also said to be oxyhsemato- crystalline, or oxyhgemoglo- 

 bine, or oxycrucrine. To this state, we have seen, corresponds No. 1 

 on the diagram on chart. But the blood can be deprived of its 

 oxygea by mechanical, as well as by chemical, means. We can use 

 the exhausting pump mechanically. Chemically we use such 

 reagents which appropriate the oxygen. These are called reducing 

 agents. Ammonium, sulphate, tin oxidul and others may be used 

 for this purpose. If we observe the spectrum whilst using these 

 agents, we immediately witness a change. " A change has come 

 over the spirit of its dream." The two oxygen-blood bands disap- 

 pear and make room for a broad dark band occupying the space 

 between D and E. Examine this band on the diagram (it is marked 

 2.) This band is called the reduction band, also the band of Stokes, 

 who first saw and described it ; it may also be called, with great 

 propriety, the band of deoxidized blood. 



Blood in a state of deoxidation is still blood, in full integrity 

 and vitality, for all that is necessary to restore its two oxygen bands 

 is to shake the blood up with air, or add some substance that will 

 give up its oxygen to the blood. Solutions of hgematociystalline 

 behave in precisely the same manner. This process can be repeated 

 many times with the same results. 



Remember these facts, for they are of the greatest importance 

 in spectrum analysis. Suppose we are called upon to analyze 

 spectroscopically a specimen of blood that has lost this most 

 important qualification ; that it cannot be reduced or deoxidized, or 

 that it is in a reduced condition and cannot be made to return to its 

 normal oxidized condition : would you not at once conclude that 

 some powerful chemical agent must have acted upon it and 

 destroyed its physical integrity ? Surely such a mode of reasoning 

 would be logical. We shall presently leai'n that this reasoning rests 

 uj)on well ascertained facts. 



AFFINITY FOR IRRESPIKABLE GASES. 



Wonderful as are the functions of the crystalline element of 

 the blood, it possesses other and dangerous qualities whereby 



