Conversation so far:
Was Havelock Ellis for or against sterilization?
Ellis was strongly opposed to the idea of castration for eugenic purposes.
Did he hae another motion in mind?
he posited that the sexual glands provided an important source of internal secretions vital for the functioning of the organism, and thus their removal could greatly injure the patient.

Question: Why did he believe that?
Self-contained rewrite: Why did Havelock Ellis believe that the sexual glands provided an important source of internal secretions vital for the functioning of the organism, and thus the removal of the sexual glands could greatly injure the patient?