Jim Harrison has lost fingers, gone into a coma and had his heart stop four times – all while doing his job. As a professional venom extractor, Harrison spends his days wrangling the world's deadliest snakes at the Kentucky Reptile Zoo, a tourist attraction and research facility that he runs with his wife. The zoo is reportedly home to the largest collection of venomous snakes in the world.

Jim wrangles the world's deadliest snakes at the Kentucky Reptile Zoo. CNBC

"The last bite I had was the South American rattlesnake," Harrison tells CNBC. "I had descending paralysis within minutes. I don't even remember leaving the parking lot here."

CNBC

Harrison and other professional extractors "milk" the venom from particular types of snakes to be used for medical research. The venom Harrison extracts through a delicate process that involves inserting the snake's fangs into a cup and rubbing its head to release the substance is used in developing pain medications and researching cancer treatments.(Though venom can only be extracted a few times in a given period, depending on the type of snake, the process is harmless to the animal.) Harrison says the reason he risks life milking snakes is to help others.

The venom extraction process. CNBC

Harrison tells CNBC he sells King Cobra venom for about $100 a gram, which is helpful, because maintaining the zoo's 2,000 snakes isn't cheap. In addition to standard expenses, Harrison spends $25,000 a year on mice alone.

Jim tells CNBC he sells King Cobra venom for about $100 a gram. CNBC

According to the Bureau of Labor Statistics, the median salary for zoologists and wildlife biologists is $62,290 per year, but Harrison doesn't take a paycheck, choosing instead to pump his earnings from venom extraction into the zoo.

As a professional venom extractor, Jim Harrison has one of the world's most dangerous jobs. CNBC