“The crisis for all mechanistic models of the iris really occured when Blumenbach . . . published a short investigation entitled De oculis leucaethiopum et iridis motu in 1786. It was dedicated significantly to Caldani with whom Blumenbach had also corresponded. In it he expressed complete dissatisfaction with all previous explanations. He claimed that no muscular structure existed, that della Torre’s observations were incorrect, that the vascular structure of the iris did not sufficiently account for its motions because, if congestion of blood really took place, this should be visible. Blumenbach could not observe it in the eyes of albino rabbits. He regarded the iris as a completely different organ from any other in the human body, and he stated that it was not subject to the laws of the latter. The motion of the iris – he wrote – derives from its own life”. (Mazzolini) Blumenbach, professor of medicine at Göttingen, is the founder of physical anthropology. He classified the various subdivisions of the human race according to skin colour and geographical habitat, and was the first scholar to show the value of comparative anatomy in anthropological research. This fairly early work by Blumenbach is a study on albinism, mutations of eye colour, and movements of the iris. There are two editions. The work was first read at a meeting of the Royal Society of Göttingen on the 9th of October 1784. A summary of the lecture appeared in the Göttingische Anzeigen von gelehrten Sachen, published in 1786. Only the second edition is dedicated to Caldani and is the only one that contains the colour-plate (which seems to be very rare and could not be found in any copy traced by Mazzolini). The plate is attractively and strikingly handcoloured and depicts the eyes of a seal and an owl. Collation: Pp 38. One engraved plate with five figures, finely hand-coloured. Binding: Contemporary boards. Provenance: Small monogram stamp on title. References: Becker, 52; Albert, 250; Mazzolini, Renato: The Iris in Eighteenth-Century Physiology (1980), pp 109-10.