( 311 ) 



was excreted by old people and by those suffering from considerable 

 muscle-paralysis, than by normal, healthy persons ^). 



However all this is no inquestionable proof that these fluctuations 

 in the excretion of creatinin are necessarily caused by changes in 

 the muscular tonus. For it may safely be granted that, although the 

 muscles contribute mostly to the formation of it, yet creatin is formed 

 in several other organs. People that are asleep, as well as persons 

 weakened by old age or other causes, show a greatly reduced meta- 

 bolism, not only in the muscles but also in other organs. Under 

 these circumstances we might be inclined to attribute the diminished 

 excretion of creatinin not entirely, nay perhaps not even in the first 

 place to the muscles, but to the weakened function of other organs. 

 Therefore I thought it desirable to examine whether a larger output 

 of creatinin can be stated by purposely intensifying the muscular 

 forms, while all other causes of changes in metabolism are excluded 

 as much as possible. 



It stands to reason that in this case vertebrates have to be ex- 

 perimented upon, no creatin being found in invertebrates. However 

 it seems impossible in animals simultaneously to cause a protracted 

 tonus of a number of muscles without producing at the same time 

 other, unreliable changes in metabolism. On man, however, the ex- 

 periment may be satisfactorily performed. Therefore I invited Mr. 

 Harkink, who had shown genuine interest in the problem, and who had 

 distinguished himself by accurate and careful work in the laboratory, 

 to subject himself to a number of experiments, proposal with which 

 he fell in most graciously. 



Our plan of research was a vei-y simple one. Leading a scrupu- 

 lously regular life and passing the greater part of the. day in the 

 laboratory, engaged on work that required little muscular exertion, 

 Mr. Harkink took every day the same amount of food, which con- 

 tained neither creatin nor creatinin. On some days, however, the 

 muscles of the trunk and the limbs were maintained in tension as 

 much as possible by assuming the so-called "stramme Haltung" every 

 time during four hours. Then we had to ascertain whether this 

 intensified muscular tonus led to a larger output of creatinin. 



The experiment began on June 20 and ended on July 20. Every 

 day his food consisted of: 



8.30 a. m. 200 gr. wheaten bread, 20 gr. butter, 50 gr. cheese, 

 400 cc. milk. 



1) Ned. Tijdschr. v. Geneesk. 1908, HI, p. 1689. 



