A scie>;tific career ^27 



Linderstrom-Lang and Olsen at the Carlsbeig l.aWoiatory. Tlu; 

 i'irst investigations of the uptake of ^^P by plants (1936 — 37) was also 

 carried out in co-operation with them. 



In 1940 Professor Hasting, who had formerly visited Copenhagen, 

 invited me to deliver the Dunham Lecture at Harvard University. 

 Denmark was occupied, and messages to the United States could be 

 sent only l)y the United States Legation in Copenhagen. When I called 

 on the minister asking him to forward a cable to Professor Hasting 

 stating, "1 shall be in New York the 21st of June," the Minister remarked, 

 "You 'd better write 'I intend to' ". It was a wise remark, as I did 

 not succeed in getting to the United States and the Dunham Lecture 

 was ultimately delivered by Schoenheimer. 



We observed, w^th Aten, that while phosphate penetrates comparat- 

 ively slowly into erythrocytes, it is incorporated very rapidly into labile 

 organic acid-soluble molecules. Thus the red corpuscles are a kind of 

 trap, though imperfect, for ^^F, a fact which makes it possible to tag red 

 corpuscles with ^^p^ re-inject these into the circulation, and from 

 the dilution figure calculate the red corpuscle volume of the subject 

 in the course of a day. This method of red corpuscle volume determina- 

 tion found an extended application. The first clinical determinations 

 could be carried out with the minute ^^p activities prepared by us by 

 irradiation of carbon disulfide with neutrons emitted by a radium- 

 beryllium source. To investigate the formation of phosphatide or of 

 casein in the milk of the goat, w^hich was the subject of the dissertation 

 of A. H. W. Aten, larger activities were needed. These were prepared by 

 Martin Kamen, put at our disposal by the great kindness of Ernest 

 Lawrence. He supplied us later also with ^^Na and ^^K. We used these 

 isotopes, among other purposes, to study the rate of interchange of 

 vascular with extra vascular ions. We were much impressed by the observ- 

 ation that within the first minute a very large fraction of the so|lium 

 ions of the circulation, for example, was replaced by extravascular 

 sodium. Today we know that the exchange-rate values obtained by the 

 tracer method supply minimum figures only. 



Max von Laue's and James Frank's Nobel Medals 



My w^ork was interrupted for only one day during the enemy occupa- 

 tion of Denmark. When, on the morning of Denmark's occupation, 

 I arrived in the laboratory, I found Bohr worrying about Max von 

 Laue's Nobel medal, which Laue had sent to Copenhagen for safe-keep- 

 ing. In Hitler's empire it was almost a capital offence to send gold out 

 of the country, and, I^aue's name being engraved into the medal, the 

 discovery of this by the invading forces would have had very serious 

 consequences for him. (Three years later the invading army occupied 



