522 



GENERAL PHYSIOLOGY 



complications are caused in the latter by the introduction of the 

 nucleus into the chain, it will be advantageous to bring together 

 the experimental facts in a schematic form, such as is shown in 

 the accompanying Fig. 260. 1 This represents a cell containing a 

 nucleus, and each arrow signifies a quantity of substances upon 

 their pathway through the metabolic circulation. 



The cell receives certain substances from the outside ; of these 

 some (a), upon meeting substances already present in the proto- 

 plasm, undergo decomposition and syntheses. Of the substances 

 resulting from these transformations some (b) are at once excreted 

 as useless, others (c) remain in the protoplasm and are there 



employed further, while a 

 third class (d) is passed on 

 tothenucleus. The nucleus, 

 moreover, obtains a por- 

 tion of the substances (e) 

 received from the outside 

 and passed on unchanged 

 through the protoplasm. 

 The substances (d-\-e) en- 

 tering into the nucleus 

 there undergo on their part 

 certain transformations, 

 from which again sub- 

 stances result ; these in 

 part (/) are given off to 

 the outside without being 

 changed by the protoplasm, 

 in part (h) pass to the 

 protoplasm to find there 

 further employment, and in part (g) remain in the nucleus itself. 



If, now, we realize that every arrow represents a sum of 

 substances, that the substances passing from the nucleus to the 

 protoplasm undergo transformations as well as those entering from 

 the outside, and that the substances arising from these trans- 

 formations are in part conveyed again to the nucleus, we obtain 

 an approximate idea of how close the metabolic connection of the 

 nucleus with the protoplasm is. 



Further, it should be remembered that in all the above 

 considerations, nucleus and protoplasm represent a great sum of 

 different, in many cases even morphologically different, bodies, 

 that in the conception " nucleus " are comprised all forms termed 

 accessory nuclei, micronuclei, etc., and that by " protoplasm " there 

 is understood the whole sum of the various products of differentia- 

 tion, even chlorophyll-bodies. Only when we consider that 

 all the various constituents of nuclear substance and, likewise, the 

 1 Cf. Verworn ('89, 1). 



FIG. 260. Scheme of cell -metabolism. The arrows 

 indicate the direction of movement of substance. 



