itative
relation to the amount of oxygen with which the haemoglobin is capable
of combining (two atoms of oxygen to one of iron). One gram of
haemoglobin crystals can combine with 1.34 cc. of oxygen. On destruction
with an acid or alkali, haemoglobin yields a pigment portion, haematin,
and a protein portion, globin, the latter belonging to the group of the
histones (Gr. [Greek: istos], web, tissue). In this cleavage the iron
is found in the pigment. By the use of a strong acid, it may be made to
yield iron-free pigment, the remainder of the molecule being much
further decomposed.

_Destruction and Formation._--In the performance of their work the
corpuscles gradually deteriorate. They are then destroyed, chiefly in
the liver, but whether the whole of this process is effected by the
liver alone is not decided. It is proved, however, that the destruction
of the haemoglobin is entirely effected there. It was for a long time
considered to be one of the functions of the spleen to examine the red
corpuscles and to destroy or in some way to mark those no longer fitted
for the performance of their work. It is proved that the destruction of
the haemoglobin is entirely effected in the liver, since both the main
cleavage products may be traced to this organ, which discharges the
pigmentary portion as the bile pigment, but retains the iron-protein
moiety at any rate for a time. The amount of bile pigment eliminated
during the day indicates that the destruction must be considerable, and
since the number of corpuscles does not vary there must be an equivalent
formation of new ones. This takes place in the red bone-marrow, where
special cells are provided for their continuous production. In embryonic
life their formation is effected in another way. Certain mesodermic
cells, resembling those of the connective tissue, collect masses of
haemoglobin, and from these elaborate red blood corpuscles which thus
come to lie in the fluid part of the cell. By a canalization of the
branches of these cells which unite with branches of other cells the
precursors of the blood capillaries are formed.

_White Blood Corpuscles._--These constitute the second important group
of formed elements in the blood, and number about 12,000 to 20,000 per
cubic mm. They are typical wandering cells carried to all parts of the
body by the blood stream, but often leave that stream and gain the
tissue spaces by passing through the capillary wall. They exist in many
va