192 



JOHN LEWIS BREMER 



appeared, but several rows of renal glomeruli are apparently 

 active, as is shown in figure 4. 



Similar figures for the chick may be interesting. At 7.5 mm. 

 twenty active glomeruli are found in each Wolffian body, with 

 many more in the earlier stages of development; the average 

 diameter is 95 micra. At 15.0 mm. the number has increased 

 to one hundred and eight glomeruli, and the diameter to 105 

 mi'cra. 



From these figures, grouped below in tabular form, two facts 

 stand out as evident; first, that the different embryos can be 

 classed as those which retain a functional Wolffian body until 

 the kidney is ready to take up the work of excretion, and those 



TABLE I 



Number and diameter of active mesonephric glomeruli at different ages, in one 



Wolffian body 



Rat 



Guinea pig 



Man 



Rabbit 



Cat 



Sheep 



Pig 



6.6 TO 10 MM. 



none 



none 



34, of 125 micra 



40, of 110 micra 



20, of 150 micra 



20+ 6, of 150 micra 



54, of 200 micra 



11 TO 16 MM. 



none 

 14, of 52 micra 

 34, of 125 micra 

 42, of 185 micra 

 26, of 165 micra 

 20+50, of 230 micra 



60, of 325 micra 



21 TO 40 MM. 



none 

 none 

 12, of 125 micra 

 34, of 200 micra 

 30, of 200 micra 

 20+50, of 285 micra 

 + kidney ' 

 80, of 325 micia 

 +kidney 



none 



none 



none 



none 

 kidney 

 kidney 



many of 

 325 micra 

 + kidney 



in which the Wolffian body disappears early, before the kidney 

 has developed active glomeruli; and second, that within each 

 of these classes, individual animals are provided with a very 

 varying amount of excreting surface, showing presumably vary- 

 ing types of metabolism. In the cat, for instance, the paucity 

 and small size of the mesonephric glomeruli up to the time 

 when the kidney becomes active, indicate a greatly reduced 

 urinary excretion as compared with that probable in the pig, 

 with its enormous and numerous glomeruli. Another example 

 of the difference in glomerular number and size in two animals 

 which early lose their Wolffian bodies is found by comparing 

 rabbit and man. 



