ARRANGEMENT OF STRUCTURAL ELEMENTS. 213 



ing their elementary constituents. For the correct 

 understanding of their form and mass this inquiry is 

 indispensable, since in the absence of such facts an 

 effort at interpretation might be fairly compared with an 

 attempt to estimate the military power of two nations 

 by weighing their armies while neglecting the fact of 

 personal strength and courage, material equipment, 

 degree of organisation, and the temper of the country. 



As we know from the previous chapters, the nerve 

 cells differ widely in the size to which they ultimately 

 attain, but at the same time in different portions of the 

 central system they exhibit peculiarities in shape and 

 structure which are characteristic. It is important, 

 therefore, to determine whether any general significance 

 can be attached to these differences. 



The relations between the diameter of the cell-body 

 and that of the neuron arising from it have been pre- 

 viously expressed by the statement that it is correct to 

 infer that a large neuron arose from a large cell -body, 

 and this relation is useful when search is made for a 

 group of cell-bodies to be associated with a group of 

 fibres. 



Most interesting on account of their wide application 

 would be the facts bearing on the relations between the 

 size of the nerve cell and the size of the animal, 

 especially when within the same species, varieties widely 

 different in size were compared. But such studies have 

 still to be made. Strictly speaking, the observations 

 alone available show a relation between the diameters of 

 the cell-bodies and either the length or weight of the 

 animals to which they belong. The size of the cells in 

 the same region in animals of different species has also 

 been studied. Table 51, taken from Kaiser, may be 

 used as an illustration of this latter case. This author's 

 studies were confined to the cells occupying the ventral 



