How to prepare an anatomical specimen?
No one was better than Ruysch at injecting dyes into the smallest blood vessels of anatomical specimens. He injected embryos, fetuses and newborn babies with such a skill that they appeared still to be alive.
The most important dye he used was a dark red (vermillion) mineral, called cinnabar, an oxide of mercury, sometimes mixed with sulfite and sheep's fat.
Ruysch made the invisible visible
William Harvey (1578-1657), a British doctor, published his revolutionary discovery of the blood circulation at the time when he was serving as a court-physician to the English King James I. He discovered that the heart pumps blood into the most delicate branches of the arteries, where he suspected capillary-like structures to be present, as he noticed that the blood did not stop at the arteries, but rather flowed back to the heart through increasingly thick veins originating from equally delicately branched veins. Unfortunately, while he suspected the existence of such capillaries, Harvey could not see them. Marcello Malpighi (1628-1694), an Italian anatomist, was the first to actually prove their existence. Ruysch visualized them using his special preparation methods. To be able to distinguish the course of veins and arteries, even in the remotest extremities, he used different colors; he filled veins and arteries with red or white 'wax-like substances'.
Dry and wet specimens
Dry specimens, like bone and certain membranes, were dehydrated by exposing them to the external environment and subsequently coating them with a kind of varnish. In addition to such methods Ruysch introduced a new method of embalming specimens (based upon techniques already known by the ancient Egyptians). But most often he preferred to use the 'wet' method, described below.
The use of alcohol to preserve human anatomy had been discovered by Ambroise Paré (1510-1590), court-physician to four French kings. Ruysch also used a recipe based on alcohol. He spoke of a 'Liquid' or 'Liquor'. We know that he used brandy from Nantes (France), an approximately seventy percent alcohol solution, supplemented for conservation purposes with, among others, black peppercorns. He closed his glass jars, those being vials with wide necks, airtight using a small sheet of shale glued to the glass' neck with resin. To complete the preservation process, a pig's bladder was often stretched over these covered vial tops.
Ruysch's specimens lasted for centuries
Ruysch's collection of anatomical specimens is now about three centuries old, but it is still available to us as it was sold in its entirety to the Russian Tsar Peter the Great and well-preserved there. To educate his subjects, the Tsar had a special museum built for this and his other collections in Petersburg, the Kunstkamera. Through the ages, 947 of the original 1500 specimen have been preserved. Ruysch predicted this himself: 'My specimens will last for several hundreds of years'.
From the vials without a stop to those with a stop
When the anatomist Karel Ernst van Baer (1792-1876) was appointed as curator of the Petersburg anatomical collections he had broken originals vials, as described above, replaced with ones equipped with a glass stop. Though regrettable that the original bottles were lost, this actually saved the specimens. The conservation of the collection remained and remains a lasting concern for all successive curators. Currently, only a few specimens are still stored in their original bottle.
Conservation and ethics
In recent years new techniques have been applied in the conservation of Ruysch' specimens, partially inspired by experience obtained in the preservation of similar specimens in The Netherlands. A major objective was to preserve the specimens as closely as possible to the situation in which Ruysch left them to us. This meant that in most cases only the preservation liquid was replaced, important as most of the original alcohol had evaporated, with a higher percentage of water remaining, because alcohol evaporates faster than water.
A few of the specimens were no longer suspended from the end of a thread (horsetail hair), but had dropped to the bottom of the vial. These specimens had to be remounted on a new horsetail hair, exactly like done by Ruysch. In several cases a specimen was transported to a new (often larger) bottle. Because these bigger vials are not for sale in Russia these had to be blown especially in The Netherlands. The conservation time interval offered a unique opportunity to chemically analyze the red dye that Ruysch had used. To have a record of what has been replaced and what not, the entire conservation process was thoroughly documented and photographed. Over 200 specimens have been treated in this manner, thanks to the financial support of the Wilhelmina E. Jansen Fund. These vials are now prominently exhibited in the beautifully restored former library of the Kunstkamera.