"It was really overwhelming when I saw that I had arms again," said the 54-year-old, who wore a sleeveless black shirt showing clearly where his new arms had been grafted.
"These are my arms, and I'm not giving them away again," he told reporters at the Munich University Clinic where he remains nearly three months after the 15-hour operation.
Merk is recovering well and can perform simple tasks such as opening doors and turning lights on and off. His ultimate goals are to eat and dress himself
-- and ride a motorcycle.
"All in all, our wildest expectations have pretty much been fulfilled," said Christoph Hoehnke, one of the lead doctors.
A total of 40 surgeons, anesthesiologists, nurses and other support staff carried out the 15-hour operation on July 25-26 to graft the donor's arms on to the body of Merk, who lost his own just below the shoulder in a combine harvester accident.
Doctors said there were good indications of nerve growth in the arms but it could take up to two years before he relearns how to use his hands.
Merk appeared at the news conference Wednesday with lower arms bandaged and supported with a series of straps attached to shoulder pads.
Merk said he was looking forward to going home after four to six more weeks of an intensive program of physiotherapy, electric stimulation and psychological counseling.
There is also still a risk that Merk's immune system will react, though doctors said so far there was no sign of them being rejected.