Dr. Ben Carson reacted tonight to the controversial Planned Parenthood video showing a discussion about the practice of using fetal body parts for medical research after an abortion.

The shocking video, shot last July, shows Deborah Nucatola, Planned Parenthood's senior director of medical research, having lunch with two undercover Center for Medical Progress activists.

Nucatola casually discusses the body parts of aborted fetuses and how they can be used for medical research. Planned Parenthood has said that it does not benefit financially from the practice.

Some in the media have defended the practice in recent days, arguing it is an important tool for medical research and downplaying the video's significance.

Carson, formerly director of pediatric neurosurgery at Johns Hopkins University medical school, said the benefits of fetal research have been "overpromised" and "under-delivered."

He called it "disturbing" that some people don't even realize the "callousness with which we are treating human life."

Carson wondered why some on the left have been so vocal about protecting species like "snail darters and little spiders," but are not interested in protecting an unborn baby.

"Yet the human being inside of that mother's womb, just beyond 10 weeks, is much more sophisticated than many of these creatures that they're trying to preserve," said Carson. 

The 2016 Republican presidential candidate said a dichotomy has been created in what should be "an almost sacred relationship" between a mother and a baby. 

"The mother is the protector of that baby and we've distorted things to the point where people believe that if the mother can't kill the baby, then anybody who is advocating that is an enemy of women. How can we be so foolish to believe such a thing?"

Megyn Kelly presented the counter-argument from Planned Parenthood's defenders, who say it's not controversial to conduct medical research on fetuses that will be aborted anyway.

Carson said he believes the video is an indication of "how far we have drifted in terms of our humanity."

In the video, Nucatola also casually referred to a “17 weeker” that she had recently aborted.

Carson expressed disbelief that some do not consider a 17-week-old fetus as a human life.

"At 17 weeks, you've got a nice little nose and little fingers and hands and the heart's beating. It can respond to environmental stimulus. How can you believe that that's just an irrelevant mass of cells? That's what they want you to believe, when in fact it is a human being," said Carson.

Watch Megyn Kelly's interview above.

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