134 



LAWSON G. LOWREY 



It would appear from this that the kidneys, throughout the 

 later part of fetal life, have about the same relative size in the pig 

 and human, but are larger relatively in the human adult. 



Agreeing with the pig and human, the kidneys appear relatively 

 smaller in the adult than in the embryo shrew, dog and chick; 

 but they are relatively larger in the adult stickleback and sala- 

 mander (Welcker and Brandt). 



The Wolffian bodies (table 1 : fig. 2) of the pig have their maxi- 

 mum very early in fetal life, probably at an earlier stage than can 

 be readily dissected. At 15 mm. they have by far the largest 

 relative size observed, — 12 . 1 per cent of the total weight. From 

 this stage the decrease is rapid. In the 18 mm. pigs they form 

 7.45 per cent; 25 mm., 4.71 per cent; 37 mm., 2.43 per cent; 

 disappearing about 125 mm. 



The Wolffian bodies present a very interesting case, as they 

 are the only structures observed (except postnatal thj'mus?) in 

 which a decrease in absolute weight takes place. 



The following table expresses the relations for this organ: 



TABLE 4 

 Absolute and relative weight of the Wolffian bodies 



Corresponding to the decrease in relative size of the Wolffian 

 bodies, there is, as might be expected, an increase in the size of 

 the kidneys. The first record of the kidnej'^s (0.22 per cent) 

 corresponds to a size of 4.71 per cent for the Wolffian bodies. 

 The maximum relative size of the kidneys (2.59 per cent) cor- 

 responds to a size of 1.41 per cent for the Wolffian bodies. At 



