The Mygdalians were known for their medical technology, which impressed many worlds and species. In 2270, the Mygdalians were in the process of being admitted to the Federation. When the USS Enterprise under Capt. Kirk arrived for a third visit, the Mygdalians came under attack from Virtili ships, who demanded their late shipment. However, they were able to work out a agreement with Kirk's and the Federation's assistance.
However, the secret of the medical technology when a clone of Starfleet Lieutenant Jason Thompson escaped from one of their facilities. The Mygdalians had somehow cloned over 2,472 Thompsons, Klingons, Andorians, and Gorns and put them into stasis. When Capt. Kirk discovered this, the Mygdalians tried to silence him. However, Kirk was able to shut down the stasis field let loose the hundreds of duplicates the Mygdalians created. After Kirk returned to the Enterprise, he offered the Mygdalians help if they stopped this practice. (TOS - Burden of Knowledge comics: "Uncertain Prescriptions", "The Burden of Knowledge")