Jacobson’s Organ or Organon Vomeronasale (Jacobsoni) is a sense organ for smell. It is an organ in pairs situated one on each side of the nasal septum in the lower and foremost region. It has no connection to the ’ordinary’ sense of smell neither in the nose nor in its reception area in the brain. It reacts on certain molecules in fluid and in most mammals on metabolites of sex hormones. The organ is necessary for initiating sexual behaviour, which in turn is followed by ’a series of events’.  If the vomeronasal organ is destroyed there will be no offspring at all. When the mammals are sniffing on individuals of the opposite sex, either it is a male or a female, they are using their vomeronasal organ. There are a few exceptions among mammals; the humans and maybe some of the higher apes have no fully developed vomeronasal organs. In man the vomeronasal is considered vestigious, i.e., only rudimentary. Fully functioning organs are demonstrated also in marsupials and reptiles. In snakes the organ reacts even on many other substances such as food.

         The vomeronasal organ consists of a soft sack filled with secretion. The medial wall of the inside is covered by a thick layer of olfactory cells and the lateral wall by a thinner layer of respiratory cells with cilia. Outside the sack is a layer of connective tissue containing many venous blood vessels with smooth muscles and a richly sympathetic innervation. There are also a great number of glands opening into the sack. Outside it all there is a stiff sack made by cartilage. The venous vessels can very quickly become constricted and due to its firm fixation to both the soft sack and the stiff one the soft sack expands and fluid is sucked into the organ. The venous vessels are similar to those in erectile organs and transmittor substances that are richly found there are also found in the vomeronasal organ (1). The soft sack has a thin duct opening into the incisive canal and is then connected with either the nose cavity or the mouth. The ducts of reptiles, e.g., are open to the mouth.

     A drawing showing the position of the vomeronasal organ is seen in figure 1.     A beautiful preparation of the vomeronasal organ of a newborn mouse may help to explain the anatomical details (see figure 2). Interesting is also that the pixture is published 1919 and prepared by Ivar Broman, Professor of Anatomy at the University of Lund, Sweden. Before Ivar Broman will be commented more thoroughly some other Nordic investigators will be mentioned.

     Ludvig Levin Jacobson, whose name is given to the vomeronasal organ, was a Danish anatomist, surgeon and veterinary physician. A Dutch embalmer, Frederick Ruysch, had in 1703 described the anatomy of a number of animals among them snakes. He found the openings of the vomeronasal organ in the palate. Ludvig Jacobson was well aware of Ruysch’ descriptions when he started his investigations. The discovery of the complete organ is dated to 1809 and the description also appeared in his thesis published in 1811. Ludvig Jacobson was born in Copenhagen 1783 and he died there in 1843. His father was ‘graveur des cachets de la Cour’, i.e., he designed seals, signets and similar things at the Royal Court of the Danish king. The father was apparently a good drawer, and so was Ludvig Jacobson. In his thesis, defended in Paris, there are a number of beautiful drawings by his own hand. The thesis was reprinted in 1950 (see figure 3) (2) and translated from the French to the English language in 1999 (3).

     Gustaf Retzius, Professor of Anatomy at the Karolinska Institute in Stockholm, demonstrated in 1894 the similarities between neurons of the olfactory epithelium in the upper part of the nose and the neurons of the vomeronasal organ and thus concluded that the latter was a sensory organ (4). Professor Gunnar Bertmar, zoophysiologist in Umeå, Sweden, carefully studied in the 1960ies the nose and especially the vomeronasal organ of a great number of vertebrates (5). Kjell Döving is a Norwegian electro physiologist who mainly has been interested in the pathways of the organ to the brain. Together with a French group of otorhinolaryngologists he has recently published findings that adult humans in around 75 % have small pits, ducts and cavities in the lower and foremost part of the nose. They conclude, however, that there are no sensory vomeronasal organs due to the lack of neurons and nerve bundles (6).

     Ivar Broman was a well-known and original Professor in Anatomy in the old University city of Lund in the south of Sweden. He was born in a small village not far from Lund in 1868. His father was a tailor, which may explain Ivar Broman’s documented well-clothed appearance. The interest for clothes continued indeed with Ivar Broman’s son Sten Broman, known as composer and from the television. Ivar Broman studied medicine in Lund, was teacher at the department of Anatomy, and defended his thesis there on embryologic development of the auditory ossicles. Obviously the thesis was of good quality because he was almost directly afterwards appointed Docent, corresponding to Assistant Professor. After some year at the Medical Faculty in Uppsala University he returned to Lund and became ordinary Professor in Anatomy there in 1909. He died from an otogenic meningitis in 1946.

     Ivar Broman’s main interest was embryology and comparative anatomy and he was soon well known in the scientific world for books and articles and his large collection of foetuses. Due to a generous donation he was able to build a new house close to the old anatomy building dedicated for embryology. His interest for embryology made him undertake much travelling to find specimens for his collection. He spent some months in Africa at more than one occasion and he became a hunter of big animals. Especially he was, of course, interested in pregnant animals. In his correspondence, saved at the University Library in Lund, can letters be found where he asks for permission to shoot that or that animal. In museums in Sweden there are still animals donated by Broman. Very formal thanks for the gift of a giraffe from a museum in Gothenburg, Sweden, is, e.g., saved among his correspondence. His travelling and shooting interested of course the newspapers in Sweden; some articles were even a bit satiric.

     When he had returned from one such Africa tour he made histological investigations of around 25 different newborn animals or foetuses of animals. He published his results in different ways (see figure 3). One publication in the Swedish language was presented at the 250 year jubilee 1918 of the University of Lund, another one in German 1919 in ‘Anatomischen Heften’ in Wiesbaden, and a third in 1920 in another German journal (7). The content of around 50 pages was almost the same in all three publications; the number of figures was somewhat different. He concluded that the Jacobson’s organ was an organ for chemical substances in fluids. Although Jacobson himself had suggested that the organ was aimed at secretion like other nasal glands, Broman wrote that Jacobson had taken under consideration that it could be a sense organ for smell and taste.

     The reports that the vomeronasal organ was important and usually necessary for starting a sexual interest for the opposite sex came first in the 1950ies. The probably first report came from France by H. Planel in 1953 (8). After that there has come a vast number of publications confirming in different way the sexual importance. Also reviews and whole books have been written, e.g., one very stimulating by Lyall Watson in 1999 (9).

     Ivar Broman’s interest for embryology and pregnant animals made him also very much interested in the evolution of man and sexuality. He indeed fulfilled the three objects in his position as Professor of a University. He did research, he educated students, and he gave speeches and wrote books and article to inform common people scientific news. Among his many books titles were, e.g., ‘The origin of man’, ‘The mystery of the sexual life’, ‘On fertilization’. Around one hundred causeries, usually first printed in newspapers, are collected in books. Many of those causeries deal with male and female relations. Frenology is one topic and Ivar Broman took an interest in racial biology. Looking at that in the modern light Broman can be very much criticized. He took part in Berlin in 1914 in the first international congress for sexual research with a lecture. Among his correspondence at the University Library there is a letter dated 1926 from the Society of Women Students in Stockholm thanking him for his lectures in a series of ‘Sexual-Ethic Lectures’. He wrote a number of textbooks for medical students and physiotherapists and some illustrations showed beautiful young girls. His ‘Topografiska Anatomi, Swedish for Topographic Anatomy’ was by the students mentioned ‘Pornografiska Anatomin’. His books, articles and many lectures on topics touching sexuality gave, of course, inspiration for many jokes and insinuation in the shows and papers produced by the students in Lund. Bearing in mind his great interest for sexual behaviour, it is ironically that he never suggested that the Jacobson’s organ had importance for the reproduction of species.

                                    Lars Malm, January 2008

                           Figure 1

                           Figure 2

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