Dogs were first raised at home at least 150 centuries ago. Since then, the dog (be) humans' best friend. Now, they have another job—to assist doctors to diagnose（诊断）cancer.
After a long-standing research of smell, a Finnish professor has said that certain (type) of cancer are able to be detected by their smell, making it possible to train cancer-sniffing dogs (help) diagnose the disease.
A professor, Jouko Vepsalainen from the University of Eastern Finland in Kuopio, has focused nitrogen compounds（氮化合物）. The compounds increase (great) when cancer cells grow in an uncontrollable way, (allow) them to be detected, the Finnish newspaper Karjalainen reported. That's where the dog, man's best friend, may step in with their keen sense of smell.
According to the news agency, researchers in Finland have tried to train dogs to do the job, but will take a dog months, even years, to tell the (different) between sick and healthy people. “Anyone knows how difficult early cancer detection is (understand) what an opportunity this is,” associate professor Anna Hielm-Bjorkman of the University of Helsinki told the Finnish media.
