386 ANIMAL PHYSIOLOGY. 
of the great complexity of this compound. The presence of 
iron seems to be of great importance. If not the essential 
respiratory constituent, cer- 
tainly the administration of 
this metal in some form 
proves very valuable when 
the blood is deficient in 
hemoglobin. 
This. substance can be 
recognized most certainly by 
the spectroscope. The ap- 
pearances vary with the 
strength of the solution, 
and, as this test for blood 
(hemoglobin) is of much 
practical importance, it will 
be necessary to dwell a little 
upon the subject; though, 
after a student has once rec- 
ognized clearly the differ- 
ences of the spectrum ap- 
pearances, he has a sort of 
knowledge that no verbal 
description can convey. This . 
; ; __ iseasily acquired. Oneonly 
Tae cryeela trom venue lost pe mat 2 needs a small, flat-sided bot- 
Ta ae ers tle and w podket.. spectro: 
scope. Filling the bottle 
half-full of water, and getting the spectroscope so focused that 
the Fraunhofer lines appear distinctly, blood, blood-stained 
serum, a solution of heemoglobin-crystals, or the essential sub- 
stance in any form of dilute solution, may be added drop by 
drop till changes in the spectrum in the form of dark bands 
appear. By gradually increasing the quantity, appearances 
like those figured below may be observed, though, of course, 
much will depend on the thickness of the layer of fluid as to 
the quantity to be added before a.particular band comes into 
view. 
When wishing to be precise, we speak of the most highly 
oxidized form of hemoglobin as oxy-hemoglobin (O-H), and 
the reduced form as hemoglobin simply, or reduced hemo- 
globin (H). 
By a comparison of the spectra it will be seen that the bands | 
