NUCLEAR SIZE OF NERVE CELLS 73 



types of cells in each stage, the number of cells measured and 

 the range of variation for each. The results are shown graphi- 

 cally in the curves which follow the table. 



A study of these results together with the plotted curves in- 

 dicates a number of fundamental conditions. In all of the 

 stages in each of the three groups of cells measured, there is a 

 wide range of variation in the size of the nucleus. This cannot 

 be charged to the normal swelling of the nucleus just before 

 mitosis, for the same variation is present in the cells of the bee 

 that had lived through the winter and in the queens studied. 

 That variation is an ever-present condition in all living things 

 is a truism, but when we attempt to indicate which organ or 

 tissue is responsible for the variation most of the observations 

 have been simply a record of the organic fact of variation. This 

 study claims that the cells and their parts such as the nuclei 

 are the variable factors that are responsible for the variation in 

 the tissue or organ. Any explanation of the cause of such vari- 

 ations has to recognize the part played by cells. It seems to the 

 writers that this natural and normal variation plays an important 

 part in explaining such conclusions as Crile comes to in regard 

 to the effects of shock. Before we can accept his conclusions, 

 we must determine what is the normal range of variation for the 

 group of cells that he studied. It would have been a relatively 

 easy problem to indicate a definite tendency beginning with young 

 adults and passing to the winter bee by simply taking some of 

 the large cells in the young adult with nuclear diameter of 12 

 micra and comparing them with those that measm-e 7.9 micra. 

 This would give a definite shrinkage with age; but when the 

 average of some forty cells is taken, the total is 9.26 micra for 

 the young adult, and 9.45 for the winter bee. We interpret the 

 difference to be due to the normal variation present in these 

 cells and do not regard the larger average for the winter bee in 

 nerve ceUs of type I as a measure of the extent of change that 

 as come with fatigue or age. 



The second inference to be drawn from these measurements 

 is the independent sequence of growth changes in these three 

 types of nerve cells. There is a more or less rhythmic variation 



