Müller left Brehm there and returned to Germany with the natural history specimens collected on his journey, and made plans for a third expedition. Unfortunately Müller ran into financial difficulties and was not able to rejoin Brehm, instead sending him funds to proceed to Khartoum with Alfred's brother Oskar and a doctor called Richard Vierthaler.
Publications
In the autumn of 1849 Müller began publication of the ornithological journal Naumannia, edited by Eduard Baldamus. He also began work on an illustrated book entitled Beiträge zur Ornithologie Afrikas (1853-1870), of which only five parts were ever published. In 1852 he purchased the natural history collection of Christian Ludwig Landbeck before the latter's emigration to Chile. Later in that same year he became director of the Brussels Zoological Garden, resigning in 1854. He then travelled to North America, and on his return wrote Reisen in den Vereinigten Staaten, Canada, und Mexiko (1864-1865).
Müller is commemorated in the scientific name of the blue-headed bee-eater, Merops muelleri.
