236 INFLAMMATION 



Ziegler says, " identical with the stimuli which excite or increase 

 functional and nutritive activity," and these are certainly in many 

 instances of chemical nature. Thus the application of various 

 irritating substances in not too concentrated a form (e. g., paint- 

 ing the skin with iodin) may lead to proliferation without causing 

 discernible degeneration of the cells. Mallory's 1 observations 

 on the phenomena of proliferation and phagocytosis show that 

 the same bacterial products which destroy the cells when con- 

 centrated, when sufficiently dilute cause proliferation of similar 

 cells. Many other instances of proliferation in response to 

 chemical stimuli might be cited, but in nearly all cases it is 

 extremely difficult to determine that the proliferation is not, 

 after all, reparative in compensation for degenerative changes, 

 and, therefore, possibly obeying some other biological law than 

 that of a simple reaction to a chemical stimulus. 



Although proper nutrition is necessary for cell proliferation, 

 yet it does not seem that excessive nourishment can lead to 

 excessive cell multiplication, or by itself cause cell proliferation 

 to take place. Oxygen and certain inorganic salts are essential 

 for cell division even in the lowest forms, and among such 

 simple organisms as sea-urchins and certain other marine forms 

 segmentation of the unfertilized ova may be incited by changes 

 in osmotic concentration, leading eventually to formation of 

 perfect larvae (J. Loeb, et al. 2 ). Potassium salts seem to be 

 particularly important for proliferating cells, and Beebe and 

 also Clowes and Frisbie 3 have found that actively growing 

 malignant tumors are rich in potassium and poor in calcium, 

 whereas in slow-growing tumors the reverse is the case. Denn- 

 stedt and Rumpf 4 also found that in hypertrophy of the heart 

 the amount of potassium is increased, while in chronic degenera- 

 tion of the myocardium the calcium and magnesium are usually 

 increased. 



Chemical studies of proliferation are lacking, except in regard 

 to the development of the embryo, etc. New tissues differ 

 from adult tissues in having a large proportion of water, and in 

 having a larger proportion of the " primary " cell constituents 

 and a smaller proportion of the various secondary constituents, 

 since these last are largely products of the activity of the adult 

 cell. Of the primary constituents, the proportion of the nucleo- 

 proteids is particularly high, and a number of interesting facts 



1 Jour. Exp. Med., 1900 (5), 15. 



2 See J. Loeb, Studies in General Physiology, Chicago, 1905. 

 3 See "Tumors," Chap. xvii. 



4 Zeit. klin. Med., 1905 (58), 84. 



