latter half of the 19th century are associated with his name. His Lectures on Development, published in 1861, at once became a standard work. But neither zoology nor embryology furnished Kölliker's chief claim to fame. If he did much for these branches of science, he did still more for histology, the knowledge of the minute structure of the animal tissues. Among his earlier results was the demonstration in 1847 that smooth or unstriated muscle is made up of distinct units, of nucleated muscle cells. In this work, he followed in the footsteps of his master Henle. A few years before this, there was doubt whether arteries had muscle in their walls – in addition, no solid histological basis as yet existed for those views as to the action of the nervous system on the circulation, which were soon to be put forward, and which had such a great influence on the progress of physiology. Kölliker's contributions to histology were widespread; smooth muscle, striated muscle, skin, bone, teeth, blood vessels and viscera were all investigated by Kölliker. The results at which he arrived were recorded partly in separate memoirs, partly in his great textbook on microscopical anatomy, which first saw the light in 1850. Albert L. Lehninger asserted that Kölliker was among the first to notice the arrangement of granules in the sarcoplasm of striated muscle over a period of years beginning around 1850. These granules were later called sarcosomes by Retzius in 1890. These sarcosomes have come to be known as the mitochondria-the power houses of the cell. In the words of Lehninger, "Kölliker should also be credited with the first separation of mitochondria from cell structure. In 1888 he teased these granules from insect muscle, in which they are very profuse, found them to swell in water, and showed them to possess a membrane." In the case of almost every tissue, our present knowledge contains information first discovered by Kölliker – it is for his work on the nervous system that his name is most remembered. As early as 1845, while still at Zurich, he supplied a clear proof that nerve fibers are continuous with nerve cells, and laying the groundwork for all later research as to the actions of the central nervous system. From that time onward he continually laboured at the histology of the nervous system, and more especially at the difficult problems presented by the intricate