entitled "Dentition in the ruminants", with some assistance from the University of Edinburgh Professor of Natural History, Robert Jameson. Jameson lent him an Ehrenberg microscope and encouraged him to develop microscopical studies from which Goodsir would later make major contributions to understanding of cell and tissue structure and function. Goodsir joined the Wernerian Natural History Society which had been founded by Jameson. Among his teachers at Edinburgh it was the anatomist Robert Knox who made the greatest impression. Knox broadened Goodsir's idea of the importance of comparative anatomy in the scheme of life and in the medical curriculum. Knox appreciated his pupil's skill and gave him normal and pathological specimens to mount and preserve. The two kept in touch with each other for many years. Museum conservator and anatomy demonstrator On 21 April 1841, he was appointed conservator of the Museum of the Royal College of Surgeons of Edinburgh in succession to William MacGillivray, who had been appointed Professor of Natural History at Marischal College, Aberdeen. Goodsir promoted the museum collections by giving public lectures featuring its specimens. and by giving lectures to medical students. His lectures on pathology in 1841 and 1842 presented his innovative ideas on cell theory which were read and later developed by the German pathologist Rudolf Virchow. He gave the first description of the stomach parasite sarcina ventriculi which demonstrated his status as a shrewd observer and innovative thinker. Two years later, he was appointed curator of the University of Edinburgh natural history collection and he was succeeded as RCSEd Museum Conservator by his brother, Harry Goodsir, who continued in this post until 1845. In May 1844, Goodsir was appointed Anatomy Demonstrator under Alexander Monro and his lectures attracted large numbers of students and did much to restore the University of Edinburgh's reputation for anatomical teaching which had suffered under Monro. The following year he published, jointly with his brother Harry, Anatomical and Pathological Observations based on his earlier lectures at the RCSEd. This book brought international recognition for his ideas on cell structure and function. The Anatomical Memoirs also contain a biography by Henry Lonsdale. Goodsir also improved the quality of the instruction in the anatomy department by extending and improving the dissecting rooms, recruiting additional staff, and giving microscopic demonstrations. Goodsir's microscopists were among the first to use the achromatic microscope. Cell theory On the basis of his studies using the compound microscope