Background
Carl Oluf Jensen was born on March 18, 1864, in Copenhagen, Denmark. The son of Peter Jensen, a pipe fitter, and Dorthea Rasmusdatter, Jensen in his boyhood was avidly interested in mathematics and astronomy.
Jensen in a laboratory.
A bust of Jensen in Frederiksberg Campus, University of Copenhagen.
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1907
educator physician scientist Veterinarian bacteriologist
Carl Oluf Jensen was born on March 18, 1864, in Copenhagen, Denmark. The son of Peter Jensen, a pipe fitter, and Dorthea Rasmusdatter, Jensen in his boyhood was avidly interested in mathematics and astronomy.
In 1882, when only eighteen years old, chance led Jensen to become a veterinary surgeon. He practiced veterinary medicine at Nimtofte in 1883, but he could not earn enough and this fact and illness compelled him to move to Copenhagen, where he began studies under the bacteriologist Bernhard Bang at the Copenhagen State Agricultural College and the physician C. J. Salomonsen.
In 1886, with G. Sand, Jensen published a study concerning gas gangrene and the edema bacillus, an anaerobic form which Pasteur in 1877 had erroneously stated to be a septic vibrio.
In 1889 Jensen was appointed lecturer at the Royal Veterinary and Agricultural College, where he remained for the next forty-five years; in 1903 he became full professor of pathology and pathological anatomy. From 1892 to 1898 Jensen also supervised the small-animal clinic and from 1898 he lectured on serology and serotherapy. Besides developing these new disciplines, he mastered abdominal surgery in the clinic and became the first veterinarian to utilize X-ray investigations in surgery.
In 1909 he founded a serum laboratory, which in 1932 was placed officially under the Ministry of Agriculture, and he continued as its superintendent until his death. From 1898 he was a member of the Veterinarian Board of Health and from 1928 its chairman. He was appointed Veterinaerfysicus, the highest veterinary office in Denmark, in 1922, succeeding Bang; in 1931 his title became veterinary director, a post he held until 1933. In these official capacities he was able to make effective contributions to the defeat of foot-and-mouth disease in Denmark and toward the export of safer Danish bacon to England.
When he became assistant at the college, Jensen continued the investigations begun with Sand. Together they demonstrated in 1888 that strangles, an infectious horse disease affecting the windpipe, was the result of a special type of pyogenic streptococcus, Streptococcus equi. During the following years he took up the problem of defects in buttermaking which led to an unpleasant taste and poor consistency in cream and butter. Inspired by the investigations of Pasteur and Emil K. Hansen of yeast, Jensen demonstrated the necessity of milk pasteurization and of pure bacterial cultures in butter production; he showed that the noxious bacteria originated in the vessels and tools used in the purification process. In 1891 he published his book on milk and butter defects which enabled farmers to save large sums of money.
In the following year Jensen demonstrated that the bacteria causing swine erysipelas can be found in both the throat and the digestive tract of healthy animals but that with reduced somatic resistance swine contract the disease; disinfection and isolation are then ineffective. In 1892 he found that vaccination with weakened cultures was the only effective prevention. During these years Jensen also investigated infectious diarrhea in cattle and braxy (bradsot), a severe infectious disease in Icelandic sheep. He developed effective serum preparations for these diseases, as well as methods for identification and differentiation of the various bacterial types and races (1897).
With the Nobelist J. Fibiger, Jensen undertook several significant investigations concerning the relation between human and animal tuberculosis - demonstrating, in opposition to the ideas of Koch, that many children are mortally stricken by animal tuberculosis bacteria (1902-1908).
Beginning in 1901 Jensen did experimental work with mice and rats on cancer transplantation; the studies showed that cancer cells survive through generations by transplantation, in 1910 he demonstrated a type of cancerous tumor in turnips, produced by Bacterium tumefaciens. The tumors could be transplanted and survive through generations of turnips not infected with the bacteria.
From 1916 to 1921 Jensen took up an endocrinological investigation, showing that the axolotl, a salamander which normally lives in the larval state and even breeds in this condition, during feeding with a thyroid substance develops to a degree never found in nature. Jensen worked out a standardized method for the effective preparation of thyroid hormone for medical use (1920).
He also founded Maanedsskrift for Dyrlaeger (“Monthly Review for Veterinary Surgeons”) in 1885 and was its coeditor until his death.
Carl Oluf Jensen is remembered as one of the pioneers of veterinary medicine and bacteriology in Denmark. His contributions, especially concerning bacteriology, are still very important, as Jensen not only has shown how to effectively prevent diseases caused by bacteria but also introduced pasteurization which has been used in mass production of milk and butter since then. His studies on cancer were also of great importance.
He received the Walker Prize (1906) for his cancer investigations and was created honorary doctor of medicine at the Copenhagen University (1910) and an honorary doctor of veterinary medicine at the Berlin Veterinary College (1912).
In 1903 Jensen became a member of the Royal Danish Society of Sciences. He also became a corresponding or honorary member of veterinary societies all over the world. In 1928 he was made the president of the Danish Cancer Committee.
In 1890 Jensen married Maria Magdalene Schmit.