curious that Laguesse even had knowledge of Langerhans’ doctoral thesis. Only 150 copies were ever printed and the vast majority of them were to be found in German Universities. Today, only very few copies have survived; Björn Hausen found only 8 original copies worldwide.
At a meeting of the biological society in Paris in 1893, Laguesse reported on the peculiar structures in the pancreas and called them ilôts de Langerhans [1, 3]. Laguesse had already previously expressed the hypothesis that there were two forms of diabetes and that one of these had something to do with the pancreas.
It is very surprising that the doctoral thesis does not contain a single drawing – in contrast to the publication on the Langerhans cells of the skin. Paul was by no means lacking a talent for drawing. He was a very capable draughtsman and painter, a talent he shared with another renowned discoverer in diabetology, Frederik Banting.
However, Paul’s “godfather” Rudolf Virchow must not have been entirely satisfied with the thesis. The grade given for this doctoral thesis was moderate, although the work is dedicated to him “in reverence and gratitude.” Also, in his rigorosum Paul receives the worst grade of the three evaluating professors from Prof. Virchow – sufficient.
On March 18 Paul Langerhans received his certificate of passing the medical examination. Initially he continued to work in Prof. Virchow’s laboratory together with his lifelong best friend Friedrich Albin Hoffmann. Hoffmann wrote in his autobiography about Langerhans: “His winning nature and his great diligence made him very pleasant to me. We had lunch together at Töpfer’s hotel (just in front of the Charité hospital in Karlsr. 7), discussed what we were working on and what interesting sections Virchow had. Soon he took me with him to his parents’ house, where his father, his stepmother and his sister were most kind to me. I soon felt very comfortable in this entourage.” We also know from Hoffmann that Paul did not belong to any student fraternity, which was extremely unusual in German academic circles in the 19th century where it was practically obligatory.
Fig. 5. The thesis of Paul Langerhans with the description of the islets, 1869 [10].
Research trips to far-flung places were very popular with academicians at the time. Flora, fauna, and all manner of ethnological pieces were brought to Europe, researched, and exhibited. Langerhans also partook in such travels, probably to follow in the footsteps of Haeckel and Virchow. Fortunately for him he had a wealthy sponsor, namely his beloved grandmother, and, on February 18, 1870, he too set off on a voyage of research, to the Near East. Beforehand, in preparation for his upcoming journey, Langerhans wrote to Prof. Ernst Haeckel in Jena:
Highly respected gentleman!
On February 18 I intend to accompany the geographer Professor Kiepert on a five-month journey to Lower Egypt, Palestine, Syria and Istanbul. I would be very pleased if this itinerary and my, despite your efforts in this subject, only rudimentary knowledge combined with good will quantum satis were sufficient to carry out any zoological or similar order from you and I therefore ask you to write to me, if you have such an order.
With warm greetings from my father,
Your grateful pupil,
Paul Langerhans.
Prof. Kiepert and Langerhans went by train to Trieste and from there, by ship, to Egypt. At a market in Cairo, Langerhans bought a selection of fish for Haeckel’s collection. They continued their journey by sea to Jaffa (Tel Aviv did not exist at that time) and onwards over land to Jerusalem.
From Kiepert’s report and sketchbook we learn in more details about this trip – they rode to Jericho, the Dead Sea, Amman, and Tiberias. Kiepert fell ill with typhoid in Jerusalem where Langerhans collected skeletal bones and became interested in leprosy. He wrote about his experiences to Virchow, who had the letter about leprosy printed in his archive [4]. The research about the different ethnic groups in Palestine was published in 1873 [5].
In June Kiepert and Langerhans continued their journey via Cyprus and Rhodes to Smyrna and then on to Constantinople. To his great regret, Langerhans’ clothes, revolver, and most of the skulls, which had been collected for Haeckel, together with other biological objects, were stolen there. But even worse was news which reached them whilst returning to Germany by ship on the Danube. As a result of the Ems Dispatch, a statement issued by Bismarck, France declared war on Prussia. The journey to Berlin now became hurried. Langerhans was called up to serve in the army of Prussia and for 3 months he worked in a military hospital in Berlin. In July, Langerhans was called to the front in France as a military physician. We know from the letters of his friend Hoffmann, how terrible the experiences of a military doctor in this war were. Although there was already the possibility of anesthesia, asepsis was not clinical practice and the infections which followed surgical procedures were catastrophic.
In May 1871, Langerhans returned to Berlin but failed to find employment. Coincidentally, at this time, an opportunity arose to accompany Prof. Karl von Kupffer, the first describer of Kupffer’s cells in the liver, on a research trip to Norway. Paul accompanied him and the two fished, for a whole month, at Arendal, located near to Oslo, to find Ascidians.
After this expedition came to an end, Paul made his way to the “Mecca” of physiology, to Prof. Carl Ludwig at the University of Leipzig. As a side-note, some years later, a young Scot named John James Rickard Macleod also trained there in physiological research. Macleod later received the Nobel Prize for the application of the hormone that is formed in the islands named after Langerhans.
Langerhans stayed in Leipzig for only a few weeks. In Freiburg, a position in pathology became available. However, this position required a habilitation. Langerhans hurriedly completed this but it contained a mere 16 pages. Virchow stepped in and wrote some letters to support the nomination. Langerhans reciprocally sent a letter of thanks to Rudolf Virchow:
Dear Uncle
You have become a prosector in Freiburg. That is, in fact I am, but it is as clear as day that I am as innocent of it as an encephalitic newborn, because without your letter Ludwig would never have written to Ecker and I would never have got this position. So allow me to assure you explicitly that I am perfectly clear about how great the disproportion between your goodness and my own merit is again here.
Your grateful pupil,
Paul Langerhans
Freiburg im Breisgau 23.10.1871
In Freiburg, Langerhans lectured on osteology and led the microscopic course. He was no longer interested in research on the pancreas – but his friend Albin Hofmann was still working on this topic in the laboratory of Prof. Frerichs (the teacher of Bernhard Naunyn) in Berlin. When Hofmann was appointed to a chair at Dorpat (Tartu in Estonian), his successor was a young Baron, born in Cologne, named Josef von Mering. Von Mering, together with Oskar Minkowski, later discovered pancreatic diabetes while at the University of Strasbourg.
At the end of 1873, Paul tried to become a professor. The dean of the faculty, Prof. Kussmaul (well-known because of his description of “Kussmaul breathing” in diabetic ketoacidosis) was in support of this appointment, but the ministry of the Kingdom of Baden refused due to him not having lectured for a sufficient
