The Microscope. 75 



green both to the right and to the left of the E line. At this stage 

 we observe a broad black band between the green and the red, 

 which is rather indefinite and bltirred in its outlines. Its position 

 is between the lines D and E, and when the solution is now 

 carefully further diluted, we observe the green tint dividing this 

 broad band into two distinct bands. The one near the D line is 

 narrower, but very finely and deeply shaded, and definite in outline, 

 whilst the second, near E, is broader but less deeply black, and 

 rather hazy in its outlines. These are the two bands of Stokes, 

 representing blood in a state of oxidation. We continue to dilute 

 carefully, and the spectrum clears up, at both its extremities permit- 

 ting all spectral tints to appear in full brilliancy. Further dilution 

 from this point has the effect to contract the bands and make them 

 hazier until finally they disappear altogether. The limit is, how- 

 ever, such, that ^uVf V^^^ o^ ^ grain of blood may yet be spectro- 

 scopically demonstrated. Solutions of hfemato -crystalline follow 

 precisely the optic phenomena of blood. 



For those who desire to convince themselves of the correctness 

 of the above statement, we would recommend to employ the blood 

 of healthy man or animal, to measure the amount of water neces- 

 sary, to proceed from step to step, especially the quantity necessary 

 to produce the oxygen blood bands in their full purity. And 

 hereby hang several lessons: First — These peculiar spectral phenom- 

 ena just described are not produced by any other fluid or substance 

 known; and where they appear in the succession pointed out, we 

 can confidently claim that the presence of blood or of haemato- 

 crystalline has been made out. 



Second— We can fairly judge of the blood under examination, 

 whether it is in a normal or abnormal condition, sencemic or other- 

 wise. Blood deficient in haemato-crystalline will require less water 

 to bring about the above described spectral phenomena. If so, we 

 may be sure that the processes of respiration, oxygenation and 

 oxidation are imperfectly performed, and vitality is at a low ebb. 

 This procedure has, therefore, not only a qualitative, but also a 

 quantitative significance. 



Certain precautions, which will be easily understood, are 

 necessary to avoid errors. We must carry on the observations 

 precisely under the same conditions, with the same spectroscope, 

 the same source of illumination, same temperature, the same dis- 

 tance of the glass tube or vessel from the slit, and the same relative 

 width of the slit; in short, says Hoppe-Seyler, "nothing at all must 



