A year later, in 1859, the Eijkman family moved to Zaandam, where his father was appointed head of a newly founded school for advanced elementary education.

From 1879 to 1881, he was an assistant of T. Place, Professor of Physiology, during which time he wrote his thesis On Polarization of the Nerves, which gained him his doctoral degree, with honours, on 13 July 1883.

In 1883, Eijkman left the Netherlands for The Dutch East Indies, where he was made medical officer of health, first in Semarang, then later at Tjilatjap, a small village on the south coast of Java, and at Padang Sidempoean in Northern Sumatra.

Eijkman was Director of the "Geneeskundig Laboratorium" (Medical Laboratory) from 15 January 1888 to 4 March 1896, and during that time he made a number of his most important researches.

Subsequently, Eijkman was able to prove that the disease was not caused by blood contamination, respiratory metabolism, perspiration, or seasonal or temperature variation.

Eijkman was unable to continue his research due to ill health, but a study by his friend Adolphe Vorderman confirmed the link between polished rice and the disease.

In addition to his work on beriberi, he occupied himself with other problems such as arach fermentation, and indeed still had time to write two textbooks for his students at the Java Medical School, one on physiology and the other on organic chemistry.

At Utrecht, Eijkman turned to the study of bacteriology, and carried out his well-known fermentation test, by means of which it can be readily established if water has been polluted by human and animal defecation containing coli bacilli.

Beyerinck's auxanographic method was applied on several occasions by Eijkman, as for example during the secretion of enzymes which break down casein or bring about haemolysis, whereby he could demonstrate the hydrolysis of fats under the influence of lipases.

[4] The Dutch Government conferred upon him several orders of knighthood, whereas on the occasion of the 25th anniversary of his professorship a fund was established to enable the awarding of the Eijkman Medal.

In Batavia, Professor Eijkman married Bertha Julie Louise van der Kemp in 1888; a son, Pieter Hendrik, who became a physician, was born in 1890.