Zoom in the invisible world

In Il Saggiatore [The Assayer] (Rome, 1623), the Pisan scientist mentioned a “telescope modified to see objects very close”. In 1625 a member of the Accademia dei Lincei and friend of Galileo, Johannes Faber (1574-1629) conferred on the instrument, until then called “occhialino”, “cannoncino”, “perspicillo”, and “occhiale”, the name of “microscope”.

The first microscopes of the Galilean type had, like the telescope, a concave lens and a convex one mounted in a rigid tube. Thanks to these simple optical devices the philosophers of nature could now gaze on a new and marvelous world, which was later to allow the development of both medical-biological disciplines and naturalist ones.

During this same period some important treatises on the construction techniques of microscopes appeared, of which La dioptrique oculaire (Paris, 1671), published in 1671, by the Capuchin monk Chérubin d’Orléans (1613-1697) is a splendid example.

In the second half of the century, remarkable results were achieved by the Italian instrument-makers Eustachio Divini (1610-1685) and Giuseppe Campani (1635-1715), while in England levels of excellence were reached by Robert Hooke (1635-1702/03).

The Dutch Antoni van Leeuwenhoek (1632-1723) built some 550 microscopes consisting of a single, tiny double-convex lens.

Still today, nine of these extraordinary instruments exist, the best of which has a magnification power of about 270 diameters.

However, some details of his drawings suggest that he owned more powerful ones, with which he could observe, starting from 1677, red blood cells, spermatozoids, rotifers, and bacteria.

Even his compatriot Jan van Musschenbroek (1687-1748), for entomological research, used a simple microscope mounted on an articulated arm that proved extremely effective. Adopted by Abraham Trembley (1710-1784), it established itself as the "aquatic" microscope of choice for observing flora and fauna from the outside of a glass vessel.

In 1740 Trembley, using this type of microscope, observed the particular behavior of the “freshwater polyp” or hydra, noting also its surprising ability to regenerate parts that had been amputated.

The next development in the simple microscope was Pieter Lyonnet's (1708-1789) "anatomical tablet", used, among others, by Lazzaro Spallanzani (1729-1799) for minute dissections. However, for entomological research, the Italian naturalist probably used the microscope designed by James Wilson (1655-1730) and built by John Cuff (c.1708-1772) c. 1742, also called "portable" or "pocket" microscope. A compound microscope only in appearance, this model enabled — among other things — Spallanzani in 1773 to discover tardigrades and their ability to experience repeated death/revival cycles.

The phenomenon, now called anabiosis, marked one of the major turning points of 18th-C. theoretical biology.

Thomas Bartholin (1616-1680) identified the lymphatic ducts; Lorenzo Bellini (1643-1704) revealed the structure and function of the kidneys, furnishing an explanation of the mechanical type; Thomas Wharton (1614-1673) formulated the theory of the glands as secretory organs; Niels Steensen (1638-1686) conducted accurate microscopic observations of muscle fibers.