Who is Dr. Isidro Cruz from The Blue Afternoon: A Novel and what is their importance?

Dr. Isidro Cruz is born probably c. 1850 - 1855 though his age is not given in the novel. He is born in Spain and thereafter immigrates to the Philippine Islands where he practices medicine in Manila at the San Jerónimo hospital. He is the senior medical practitioner at the hospital. He is extremely racist and considers himself superior to everyone not born in Spain. This attitude borders on a Naziesque view of the world and Cruz frequently performs grisly medical experiments on animals or humans that he considers expendable.