Karl Ernst von Baer in Italy (1845-46) and his

relationships with Italian naturalists

Karl Ernst von Baer’s 225° jubilee

1792 - 2017

von Baer’s travel in Italy in 1845

Filippo De Filippi

1814 - born in Milan on 20th April

1836 – takes his degree in Medicine at the University of Pavia, where he remains to carry out scientific re-search as an assistant to the chair of Zoology

1837-40 – works at the University Museum founded by LazzaroSpallanzani and prepares a catalogue of the snakes

1840 – shifts to Milan to work at the Natural History Museum

1848 – gets the chair of Zoology at the University of Turinand delivers the inaugural lecture “On the importanceof zoological studies”

1862 – takes part in an official mission sent to Persia as the director of the scientific group. Upon his return to Italy he writes a number of articles on the flora and fauna of Persia and publishes his diary of theexpedition “Notes of a voyage to Persia”

1864 – made a senator of the Kingdom of Italy, on 11th January gives the public lecture “Man and the Apes” by which he popularizes the Darwinian theory in Italy for the first time

1865 – embarks on the warship “Magenta” to take part in agovernment-sponsored scientific voyage to circum-navigate the globe and collect plant and animal specimens

1867 – dies on 9th February at Hong Kong

Route of the ship "Magenta"

Giandomenico Nardo

1802 – born in Venice on 4th March

1807-20 – attends the primary and secondary school at theSeminary of Chioggia and is introduced to the studyof natural sciences by his uncle, abbot Giuseppe M. Nardo

1822 – enrols on the courses of Medicine at the Universityof Padua and starts to cooperate with his professor of Natural History Andrea Renier

1827 – takes his degree in Medicine

1828 – becomes assistant to the chair of Natural History withthe task of reorganizing the zoological collections

1831 – revises the systematics of the Adriatic sponges andshifts to Venice

1832 – goes to Vienna to improve his medical qualificationsand study the zoological collections of the ImperialMuseum

1833 – goes back to Venice and establishes the new class ofSpongiaria

1840 – becomes a member of the Royal Institute of Veneto ofSciences, Letters and Arts

1849-65 – director of a charitable institution for abandonedchildren

1868 – director of the Committee of Agricolture and Fish Farming

1877 – dies in Venice on 7th April

Chondrosia reniformis (Nardo, 1847)

During his stay in Trieste in 1845-46 von Baer established contacts with several local naturalists, including the botanists

Bartolomeo Biasoletto (1793-1858) and Muzio de Tommasini (1794-1879), and Heinrich Koch ( 1815-1881), an amateur

zoologist with special interest in marine invertebrates. In 1846 von Baer helped Koch in arranging his collection of

zoological specimens which became the core of a private museum, the "Zoological-Zootomical Cabinet“, where it was

exhibited free until the end of 1848. Koch was the first director of the Museum. In 1852 the Cabinet with its library passed

under the aegis of the city of Trieste. In 1855 it was named City Museum of Natural History "Ferdinand Maximilian“, in

honour of the brother of Emperor Franz Joseph.

Mauro Rusconi

1776 – born in Pavia on 18th November

1796 – joins the Napoleonic army and enrols on theFaculty of Medicine at the University of Pavia

1797 – commissioned into the artillery as a captainat the stronghold of Mantova

1799 – goes back to Pavia to resume his studies asMantova is reoccupied by the Austrian army

1800 – the University of Pavia reopens at the return of Napoleon

1806 – takes his degree in Medicine

1811 – becomes researcher and teaching assistant tothe chair of Physiology and Comparative Anatomy

1812 – shifts to Paris to attend Georges Cuvier’slessons of Comparative Anatomy

1813-19 – prosector to the chair of Physiology and Comparative Anatomy at the University of Pavia

1819 – publishes a monograph on Proteus anguinus

1820 – refuses the chair of Universal Natural Historyand Technology and loses every position at theUniversity

1821-47 – publishes studies on fertilization and devel-opment of amphibians and fish and the lymphatic system of amphibians

1835-39 – publishes five letters to H. Weber to criti-cize von Baer’s embryological work

1849 – dies at Cadenabbia near Como on 27th March

With Prévost and Dumas (1824) we have the first accurate and

seriously analytical description of segmentation in the egg……the

manner in which von Baer dismissed this work and the work of

Mauro Rusconi seems to me to besmirch von Baer’s magisterial

reputation…

Prévost and Dumas were fully aware that the furrows that they

observed on the surface of the developing egg led to its complete

division…..To assert that Prévost and Dumas dealt only with

surface phenomena is, if one is charitable, a misreading of their

paper, or, if one is less so, a deliberate mis-representation of it.

There is no doubt whatever that Rusconi was fully aware of what

was going on…[he gave] a perfectly accurate description of

segmentation in the fertilized egg. It is therefore a matter of more

than a little surprise that von Baer in his notable paper on meta-

morphosis in the eggs of anurans summarily dismisses the earlier

work …in such a cavalier fashion….

Rusconi agrees with von Baer about the impossibility of ‘prefor-

mation’, but points out that the case against ‘preformation’ has

already been made by Prévost and Dumas.

von Baer’s paper was received by German scientists with acclaim,

and virtually all textbooks refer to him as the discoverer of the

biological significance of furrow formation and segmentation. The

true position appears to be that the discoverers were Prévost and

Dumas, and, with even greater clarity, Rusconi. The best that can

be said of von Baer’s paper is that he elaborated on their discov-

ery and provided a great deal of additional experimental detail.

Annales des sciences naturelles, t.2;

1824Müllers Archiv für Anatomie, Physiologie

und wissenschaftliche Medizin, 1834

1826

Rusconi von Baer

According to Rusconi the unfertilized egg, coincident with the germ, is just a vesicle filled

with an amorphous fluid. Fertilization triggers an internal movement leading to a peculiar

type of crystallization which produces the elementary molecules of the major systems. The

furrows at the surface are due to the pressure of water and their number increases in relation to

the number of the inner dividing masses of the germ. When the furrows are obliterated the

germ appears to be transformed into a granular mass.

This crystallization could be called animalization, since fertilization endowes the germ with a

peculiar property which allowes him to pass from the liquid to the solid state and take gradual-

ly the animal form.

According to von Baer the egg is an organized entity standing in latent life. In the frog the

germinal layer is coincident with the pigmented cortex, which spreads all over the egg [during

gastrulation]. The furrows are nothing but the limits beween the dividing masses, which split

by dichotomous division. This division is brought about by a force acting from the surface

towards the inside, but it involves also the whole inner mass. Each dividing mass behaves as

an independent entity which, however, is still "part of the dominant unity". This subordi-

nation to the whole is revealed at first by the general pattern of division, but it is maintained

also in advanced stages. Divisions do not cease when the furrows are no more evident, but

they go on during the pause which precedes the embryo formation as well during the growth

of the embryo itself. "The self-divisions follow each other so long until the countless new

individualities have extremely less importance and appear to be only elementary parts of

a new individuum – the previous individuum will be dissolved by a vital process, albeit

without destroying him completely, and a novel one will be made by his fragments".

The view of Rusconi belongs to the antivitalistic attitude which dominated during the second

half of the XVIII century and tried to explain the properties of life with chemical and physical

laws. The elementary units of life were considered to be either particles (Maupertuis) or organic

molecules (Buffon) which aggregated by a process akin to crystal formation. However, Buffon

noticed that embryonic structures grow not only by addition of molecules at the surface, but in

three dimensions, as if they followed an "internal mould". Development, then, should occur by

aggregation as well as by inner modification.

The analogy between crystals and the elementary units of life (either fibres or globules or

"cells") was widely accepted during the first decades of the XIX century. In France it was

supported by Dutrochet and Raspail, who asserted that elementary vesicles or cells were pro-

duced by a crystallization sui generis, i.e. by a superimposition of molecules which led to sac-

cular instead of angular shapes.

This model influenced Theodor Schwann, who is often considered to be the founder of the cell

theory together with Matthias J. Schleiden. However, these authors’ideas about the cells and

their origin were quite different from the current ones. As described by Schwann (1839), novel

cells arise inside a fluid called cytoblastema by a process of concentric addition. The nucleus is

formed around a previously formed nucleulus, and then, the cell is laid around the nucleus. This

exogenous formation of cells is comparable to the growth of crystals inside a solution, one

major difference being the addition of selected organic molecules between the previously exist-

ing ones (intussusception).

Albrecht von Haller (1708-1777)

In comparison to these views, von Baer (1834) put forth a truly revolutionary idea:

"I consider the fragmentation of the yolk mass as the prototype of every histological

building. I do not believe that in the muscle elementary fibres settle near each other,

but that the previously formed ones go on to divide. The same occurs in the nervous

fibres".

Further insight into the mechanism of cell division came from the studies von Baer carried out in

Italy (1845-46). In the semi-transparent sea urchin eggs he could observe that the nucleus was the

first to divide and the direction of its division determined the position of the cleavage plane

between the sister cells.

Contrary to the opinion of Schleiden, Schwann and other students, e.g. Albert von Kölliker who

in 1845 remarked that "nuclei and cells multiply by endogenous procreation", these observations

showed that every nucleus derives from a nucleus and a cell never formes either inside or

outside a previous cell.