GASSERIAN GANGLION! ALBINO RAT 243 



the nuclei grow appreciably, as can be seen by the columns 

 giving their respective diameters in table 7. 



THE RELATION BETWEEN THE RELATIVE VOLUMES OF THE 

 GANGLION CELLS AND THE RELATIVE AREAS OF THE HEAD 



It was noted by Levi ('08), by Busacca ('16), and by Donald- 

 son and Nagasaka ('18) that the volume of the spinal ganglion 

 cells increases during later postnatal growth at the same rate 

 as the area of the body surface. I have attempted to determine 

 whether or not the cells of the gasserian ganghon, a cranial 

 ganglion, differ from the spinal ganglion ceUs in respect of this 

 relation. 



In the present case the relative area of the head was used 

 instead of that for the entire body surface, for the simple reason 

 that the fifth nerve innervates the skin and other structures in 

 the head. Just as the relative area of the body surface is found 

 from the squares of the cube roots of the body weight, I have 

 estimated the relative area of the skin of the head from the 

 squares of the cube roots of the weight of the head.^ 



The values for the weight of the heads were calculated from 

 the table of Jackson and Lowrey ('12) for the several body 

 weights obtained in the present investigation. 



In the first column in table 8 are given the squares of the cube 

 roots of the head weights from which the series of ratios were 

 obtained. Table 8 shows the area of the head as growing much 

 more rapidly than the volume of the ganglion cells. 



1 It is recognized of course that the distribution of the fifth nerve is to the 

 anterior portion of the head only and that the whole head therefore includes a 

 large surface outside of the area supplied by this nerve. Also it is evident that 

 the fore part of the head changes in shape with age. On considering all the rela- 

 tions involved, it would appear that, owing to the increase in the specific gravity 

 of the head tissues with age, the computation here made would give in the older 

 heads, with a higher specific gravity, a computed area which was too large. At 

 the same time the change in the form of the head, which becomes more pear- 

 shaped and less spherical with advancing age, brings about an increase in the 

 actual area of the head in relation to its weight, and we have considered this as 

 balancing the error introduced by the change in the specific gravity of the parts. 

 The direct measurement of the areas of the head at different ages is of course 

 needed for a precise discussion of the question here raised. 



