490 A .H . Estahrook 



INTRODUCTION 



Most Studies of growth have been made upon organisms com- 

 posed of a multitude of cells, so that the growth observed is a 

 complex resultant of the growth of the component cells. It is 

 evident that in producing such a resultant, the method of growth 

 of each single cell might be very different from that of the organ- 

 ism as a whole. The present paper examines the growth of a 

 single cell, as affected bv various agents, particularly chemicals. 



There have been but few studies of the growth of single cells, 

 jenningsi ('08) studied the normal growth of the infusorian 

 Paramecium, showing that it follows a curve that is similar, in a 

 general way, to that of the growth of a multicellular animal having 

 determinate growth. Popoff ('09) investigated the relative 

 growth of nucleus and cytoplasm in a number of infusoria. Balls 

 ('08)) examined the growth of the S(jre-shin- fungus, particularly 

 the effect of temperature upon it. In this organism the growth 

 of the cell is indeterminate, as La many of the higher organisms. 



The common infusorian Paramecium has served as object of 

 the present study. The normal growth of Paramecium is thus 

 summarized by Jennings: - 



In the following investigation, I have endeavored to find out 

 some of the factors determining growth in Paramecium, and to 

 discover whether size may be permanently modified by external 

 conditions. The effect of the following chemicals upon the growth 

 of Paramecium has been studied: sodium chloride, the alkaloids 

 nicotine and strychnine nitrate, and alcohol. The growth in pure 

 water, containing no food or salts, has likewise been studied. 



I wish here to acknowledge my indebtedness to Prof. H. S. 

 Jennings, under whose direction the work was done, for valuable 

 suggestions and criticism. I also wish to thank Prof. B. E. Living- 

 ston for his interest in the experiments on osmotic pressure. 



1 Loc. cit., page 441. 

 ^Loc. cit., page 448. 



