The microscope from Galileo to the Accademia del Cimento

The compound microscope
The first microscopes were produced around the same time as the telescope. They also had two or more lenses, but with an objective lens of shorter focal length.  The invention is attributed to Galileo (1564-1642), although, in the 17th century, the claim was contested by others. 

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.

The fame of Galileo's optical instruments inspired a search for new solutions. In the 1620s, microscopes of the Keplerian type, composed of convex lenses that furnished a reversed image, were developed.

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 simple microscope
Although the compound microscope originated with two or more lenses, the first research on insects, worms and organisms invisible to the naked eye was conducted with the simple microscope, which, coming into use in the second half of the 17th century, provided greater magnification and a higher degree of resolution.  

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.

Microscopic anatomy
Microscopic anatomy began during the course of the 17th century with Federico Cesi (1585-1630) and Francesco Stelluti (1577-1651) in the Apiarium (Rome, 1625), a work covering a single folio of extraordinary size, containing detailed descriptions of naturalist, historical-erudite and literary nature on bees. Later, Giovanni Battista Hodierna (­1597-1660) published, in L'occhio della mosca (The fly's eye) (Palermo, 1644), a text dedicated to the anatomy of insects, a masterly example of naturalist research conducted with the aid of the microscope. Marco Aurelio Severino (1580-1656), in his Zootomia Democritaea (Nuremberg, 1645), justly considered the first treatise on comparative animal anatomy, proposed an atomistic conception of animal structures developed on the basis of microscopic observation.

Microscopic anatomy was however developed in all of its potentiality by Marcello Malpighi (1628-1694). As Galileo had launched exploration of the great machine of the universe with the telescope, so Malpighi aimed to reveal the hidden structure of the machine that was the human body with the microscope.

He observed the alveolar structure of the lungs, the papillary receptors on the tongue, the connection between arterial and venous blood vessels, identified the red blood cells and described precisely the first stages in the embryonic development of a baby chick.

The combination of “thin” anatomy and microscopic magnification soon led to a succession of remarkable discoveries.

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.

Francesco Redi (1626-1697) illustrated the extraordinarily complex organization of insect life;Thomas Willis (1621-1675) and then Albrecht von Haller (1708-1777) studied the structure of the nervous system and the dynamics of neuro-muscular functions.

Credits: Story

Curator: Sara Bonechi

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