He was especially successful in making vases and circular dishes of vitro di trina; one of the latter in the Correr collection at Venice, believed to have been made in his glass-house, measures 55 centimetres (nearly 23 in.) in diameter.
The sun shining, he fixed a round glass speculum (orbem e vitro) in a window-shutter, and then closing it the images of outside objects would be seen transmitted through the aperture on to the opposite wall, or better, a white paper screen suitably placed.
Metchnikoff and Bordet subsequently devised means by which a similar change could be produced in vitro, and analysed the conditions necessary for its occurrence.
It is quite evident that bactericidal action as tested in vitro outside the body does not correspond to the degree of immunity possessed by the animal under natural conditions.