METABOLISM AND THE DISTRIBUTION OF MATERIAL 235 



There are, moreover, the interesting observations of P. RONA and 

 D. TAKAHASHI,* HOLLINGER* and E. FRANK* concerning the dis- 

 tribution of sugar between blood corpuscles and plasma. 



If we go further and observe the distribution of the other ele- 

 ments of the organism, the albumins, nucleins, elastin, the lipoids, 

 etc., we approach the greatest problems of anatomy and histology 

 and set out upon a boundless and uncharted sea. Possibly we shall 

 learn more of these things in the not too distant future. 



The Circulation of Material. 



Both the plant and the animal organism are surrounded by mem- 

 branes or pellicles, which separate them from the outer world. These 

 membranes are more or less permeable to water and crystalloids, but 

 normally, they are impermeable to colloids. Even though this last 

 fact were not experimentally demonstrated, we should assume it a 

 priori, because if the dissolved colloids could leave the organism, the 

 loss of material would mean death. To demonstrate the correct- 

 ness of our conclusion, we need but mention a pathological con- 

 dition, albuminuria. In this condition the kidney becomes permeable 

 for serum-albumin, and it is one of the physician's most important 

 duties to compensate for the continuous loss of substance by proper 

 dieting, so that no impoverishment of the tissues as regards al- 

 bumin occurs. 



Within the organism also, there are many such partitions; they 

 serve to organize activity, to guide the food along certain paths 

 (arteries, veins, vascular bundles of plants) and to collect secretions 

 (urinary bladder, gall bladder). 



The substances necessary to support life must accordingly enter 

 the organism as gases or crystalloids. In the case of plants, C0 2 

 enters through the leaves; other foodstuffs, water and most of the 

 inorganic salts (nitrates, phosphates, potassium and lime salts, 

 etc.), enter through the roots. These substances are at the outset 

 very diffusible and need na preparation. It is otherwise in the case 

 of animals, which require outside of water but few crystalloids 

 (sugar, salts) and are chiefly sustained by colloids (vegetables and 

 meat). In order to enter the organism at all, these substances 

 must first be changed to a crystalloidal condition. This is accom- 

 plished by enzymes; the diastatic ferments split starches; pepsin 

 and trypsin split protein; and herbivorae have ferments which are 

 able to change even cellulose into a crystalloidal condition, etc. 



In like manner only gases or crystalloids can leave the organism 

 (expired CO2, urine, perspiration). 1 



1 Feces, etc., do not, strictly speaking, leave the organism any more than 

 diatoms which have been surrounded by an amoeba and then cast out (they are 

 evacuated from a tube which passes through the animal). 



