{ 1 } - Generally speaking, any particular human functional capacity can be diminished when necessary for the good of the whole person; that is, so that the person can better exercise all other human functions.
{ 2 } - Primary or basic functional capacities can be sacrificed to promote even more important capacities, even when it is not necessary to preserve the life of the whole person.
{ 3 } - Primarily, human health is not merely a matter of organs but of capacities to function humanly.
{ 4 } - Secondary functions can always be sacrificed to more basic ones. (A finger can be removed to save the use of the hand.

The opposite is true. Thus the Church disapproved of the action of Origen, the great third century theologian, who castrated himself (sacrificed a primary, basic functional capacity) in hopes of freeing himself from sexual distractions for study and teaching (more important capacities). See p. 221. On the other hand, it would be acceptable to be castrated in order to stop the spread of cancer and preserve one's life.