(Reuters)

This story has been updated.

Ben Carson defended the use of fetal tissue for medical research Thursday, after a blog published excerpts of a 1992 paper describing work the neurosurgeon-turned-presidential candidate carried out using aborted fetuses. In an interview with The Washington Post, Carson called the revelation "desperate," and ignorant of the way medical research was carried out.

"You have to look at the intent," Carson said before beginning a campaign swing through New Hampshire. "To willfully ignore evidence that you have for some ideological reason is wrong. If you’re killing babies and taking the tissue, that’s a very different thing than taking a dead specimen and keeping a record of it."

Carson, who has risen in primary polls since last week's debate, is among the Republicans who've condemned Planned Parenthood after undercover videos revealed executives in the organization coldly discussing the extraction and distribution of tissue from aborted fetuses. In a July interview on Fox News, after the first videos broke, Carson said that there was “nothing that can’t be done without fetal tissue" and that babies aborted at 17 weeks were clearly human beings.

That inspired Jen Gunter to excavate a 1992 paper, co-authored by Carson, in which doctors described how they applied "human choroid plexus ependyma and nasal mucosa from two fetuses aborted in the ninth and 17th week of gestation." That, wrote Gunter, was quite the contrast from Carson's 2015 denunciation of fetal tissue research.

"Could he think his own research was useless?" Gunter asked. "If it was non-contributory to the field why was it published? Maybe he forgot that he’d done the research on fetal tissue?"

Critics of Planned Parenthood are going after the organization's federal funding. Here are the ins and outs of the organization, the controversy and what may happen next. (Gillian Brockell/The Washington Post)

Carson had not forgotten and considered the type of research he did to be useful. "When we obtain tissue like that, we want to know what the origin of that tissue is developmentally," he said. "Knowing that helps us determine which patients are likely to develop a problem. It’s one of the reasons why at the turn of the last century, the average age of death was 47. Now, the average age of death is 80. Using the information that you have is a smart thing, not a dumb thing."

Asked if fetal tissue research should be banned, or if it was immoral, Carson said no.

"Bear this in mind about pathologists," said Carson. "Regardless of what their ideology is, when they receive tissue, they prepare the tissue. They label it. They mark how it got there. Regardless of whether it’s from a fetus or someone who’s 150 years old, they bank them in tissue blocks. Other people doing comparative research need to have a basis. When pathologists receive specimen, their job is to prepare the specimen. They have no job opining on where the tissue came from."

There was no contradiction between this science and Carson's pro-life views, he said. "My primary responsibility in that research was when I operated on people and obtained the tissue," said Carson, who noted that he has not used fetal tissue samples since then. "This has everything to do with how it’s acquired. If you’re killing babies and taking the tissue, that’s a very different thing than taking a dead specimen and keeping a record of it."

Asked if Planned Parenthood should cease its fetal tissue distribution, Carson demurred. He still favored defunding the group, but would not call for the end of fetal tissue research so long as the fetal tissue was available.

"I may not be completely objective about Planned Parenthood, because I know how they started with Margaret Sanger who believed in eugenics," he said. "But it would be good for the public to understand this whole aspect of medical research."