from
The Collaborative International Dictionary of English v.0.48
Disassimilation \Dis`as*sim`i*la"tion\, n. (Physics)
The decomposition of complex substances, within the organism,
into simpler ones suitable only for excretion, with evolution
of energy, -- a normal nutritional process the reverse of
assimilation; downward metabolism; -- now more commonly
called {catabolism}.
[1913 Webster +PJC]
The breaking down of already existing chemical
compounds into simpler ones, sometimes called
disassimilation. --Martin.
[1913 Webster]