No. 581] GERM CELLS AXD SOMATIC CELLS 287 



retical bearing. E. Hertwig 3 also regards the death of the 

 somatic cells as unavoidably determined by their organi- 

 zation which precludes necessary readjustments. 



Minot 4 likewise held the life of somatic cells to be 

 limited in duration and he ascribed this limitation to 

 changes in cell structure, leading to a differentiation of 

 the cytoplasm during the process of life ; a change which 

 he designated as cytomorphosis. 



Within the last 14 years certain facts have been estab- 

 lished which are contrary to this conception of a radical 

 difference between germ and somatic cells as far as their 

 potential immortality is concerned. Experimental inves- 

 tigations in tumor growth have furnished these facts. 

 Before we state these results we have first to consider, 

 how far tumor cells can be regarded as somatic cells. We 

 consider here malignant tumors (cancers). They origi- 

 nate at various parts of the body, often under the influ- 

 ence of long-continued irritation. In many cases we can, 

 if we obtain sufficiently early tumors, trace the trans- 

 formation of the normal into the abnormally proliferating 

 (tumor) tissue. This has been, as was to be expected, 

 especially observed in the case of superficial cancers, 

 where early stages of tumors are most likely to be en- 

 countered, for instance, in cancers of the skin, of certain 

 mucous membranes, but also occasionally in internal can- 

 cers as in those of the stomach. In such cases the cancer 

 cells are undoubtedly the offspring of ordinary somatic 

 cells. There are, however, tumors, so-called teratomata, 

 which in all probability take their origin in the germ 

 glands and other parts of the body from parthenogenet- 

 ically developing ova. But while these latter tumors do 

 not originate from somatic, but from germ cells, the tumor 

 cells themselves are no longer germ cells, but somatic cells 

 in the same sense as the ordinary tissue constituents 

 which also are derived from germ cells. We can therefore 



