318 PHYSIOLOGICAL DEVELOPMENT. 



* * * " the urine assumes a saffron tint in consequence of 

 the elimination of the colouring matter by the kidneys ;" and 

 afterwards "the sweat, the milk, the tears, the sputa" become 

 yellow. We have clear proof, then, that biliverdine is an 

 excrementitious matter, which, if not got rid of through the 

 liver, makes its way out, to some extent, through other or- 

 gans, producing in them more or less derangement — itching 

 of the skin, and sometimes, in the kidneys, a secondary 

 disease. That of the bile discharged into the intestine, only 

 some components are re- absorbed, is demonstrated by the fact 

 that when injected into the blood, bile destroys life in less 

 than twenty-four hours ; and that biliverdine is not among 

 the re-absorbed components, is shown both by the persistence 

 of the colour which it gives to the substances in the intestine, 

 and by the absence of that jaundice which, if re- absorbed, 

 it would produce. Hence we are warranted in classing bili- 

 verdine as a waste product. And considering that the bile- 

 cells, where they first make their appearance among animals, 

 are distinguished by the colour ascribable to this substance, 

 we may fairly infer that the excretion of biliverdine is the 

 original function of the liver. 



One further preliminary is requisite. We must for a 

 moment return to those physico-chemical data, set down in the 

 first chapter of this work (§§ 7 — 8.) We there saw that 

 the complex and large-atomed colloids which mainly compose 

 living organic matter, have extremely little molecular mo- 

 bility ; and, consequently, extremely little power of diffusing 

 themselves. Whereas we saw not only that those absorbed 

 matters, gaseous and liquid, which further the decomposition 

 of living organic matter, have very high diffusibilities ; but 

 also that the products of the decomposition are much more 

 diffusible than the components of living organic matter. And 

 we saw that, as a consequence of this, the tissues give ready 

 entrance to the substances that decompose them, and ready 

 exit to the substances into which they are decomposed. Hence 

 it follows that, primarily, the escape of effete matters from the 



