( 381 ) 



Consequeutly there is a very strikiug agreement between the 

 contraction of the Madder epithelinm (containing the nucleus) and the 

 red blood-eorpuselos (void of nucleus), effected by the same salt- solution. 



Influence of Urea. 



Considering the above-described behaviour of bladder-epithelium with 

 respect to Na CI, it appeared further of importance to me to ascer- 

 tain whether this applied to urea, a substance which is present in 

 large quantities in the urine of omnivora, and which according to 

 determinations of the freezing-point made by me, constitutes in man 

 more than a third part of the hygroscopic power of the whole of 

 the urine. 



The question interested me, especially from a general physiological 

 point of view. As is well known, Grijns and Köppe observed that 

 red blood-corpuscles let urea easily pass through them. And I should 

 not be surprised if that were the case with most of the other cells 

 too. It could not but appear fitting to us, that the cells should be 

 able to get rid of urea, the principal final product of albumen analysis. 

 But it would certainly appear unfitting, if the urea should be able 

 as easily to penetrate through the wall of the bladder. In that case 

 the bladder would answer very badly to its purpose as a reservoir 

 for the refuse products, of which the urea constitutes an important 

 part, and one not without danger to the organism. 



The question then arose : does the bladder-epithelium, in contrast 

 with the red-blood corpuscles possess the power of refusing a pas- 

 sage to the urea? In order to answer this question we prepared 

 urea-solutions, isotomic with NaCl 0.7, 0.9, 1.2 and 1.5%, caused 

 them to act on the bladder-epithelium, but obtained only a compa- 

 ratively slight influence on the volume. On a longer action the 

 difference between the volumina was ; in other words, in four 

 different solutions the epithelium exhibited the same volume; the 

 urea-solutions had thus penetrated as such into the cells, 



Formerly we had observed that red-blood corpuscles are destroyed 

 in pure urea- solutions i) ; perhaps the epithelium was injured too by 

 such solutions. We, therefore, resolved, instead of pure urea-solu- 

 tions to take mixtures of Na CI and urea-solutions, which were, two 

 and two, isotonic with each other, the more so, because in the urine 

 there is much Na CI besides urea. 



Here is an experiment that speaks distinctly. 



') Archiv. f. Anat. u. Physiol. Physiol. Abth. 1896. S. 4S1. 



