II 
THE PIGMENTS OF ORGANISMS 
29 
the contained iron, it possesses the power of forming 
a loose combination with oxygen, and so of acting as 
a respiratory pigment. Of its origin little is known, 
but there seems to be some reason to believe that in 
development it arises from the chromatin of the 
nucleus. In a recent paper on iron-compounds in 
animal and vegetable cells by Dr. Macallum, the 
author puts forward the theory that the chromatin, 
that part of the nucleus which readily takes up stains, 
is an iron-holding nucleo-albumen. This chromatin 
has the power of fixing free oxygen, and the forma¬ 
tion of haemoglobin results in the conversion of the 
nuclein into the pigment haematin ; the substance re¬ 
taining its primitive power of forming a combination 
with oxygen. Further, Dr. Macallum regards the 
diminished amount of haemoglobin in the blood in 
anaemia not as the prime cause of the disease, but as 
one of the results of the deficiency of iron-containing 
compounds in the nuclear chromatin ; this deficiency 
being the prime cause of the various symptoms of the 
disease. The distinction may seem unimportant, 
but it is not so in reality ; lor if Macallum’s view be 
correct, it carries us one point further. Anaemia is 
recognised in our own species by the pallor of the 
lips and skin produced by the diminution in the 
number of red blood corpuscles ; it is therefore 
natural to conclude that the disease is caused by 
the insufficient amount of haemoglobin present. If, 
however, it is proved that this absence of haemoglobin 
is itself merely a consequence of something deeper 
which affects the whole organism, we are at least a 
little nearer the problem of the primary meaning of 
haemoglobin. 
