190 JOHN LEWIS BREMER 



In human embryos of 37.0 mm. to 40.0 mm. there are usually 

 about a dozen mesonephric glomeruli on each side, some under- 

 going degeneration, others showing every sign of normal activ- 

 ity, with bulging epithelial plates over fully distended capillaries, 

 and no change of the flat epithelial cells of Bowman's capsule 

 to a cuboidal layer, which is one of the characteristic signs of 

 degeneration, according to von Winiwarter. By reconstruction 

 1 have been able to follow the tubules from certain of these ap- 

 parently normal glomeruli to the duct. In each case, at the 

 junction of the tubulus collectivus with the tubulus secretorius, 

 the lumen suddenly narrows and the epithelium becomes in- 

 distinct, stains lightly, and is obviously changed from the nor- 

 mal. In other tubules actual breaks occur at this spot, as Felix 

 noted; but 1 think he has been misled by the fact of these actual 

 breaks at degenerated portions of some tubules to the con- 

 clusion that in all the tubules there is a loss of continuous lumen. 

 The lumen is present in some tubules, and these are probably 

 the ones found acting as ductuli efferentes in the few cases 

 where the rete joins the corpuscle, instead of the tubulus col- 

 lectivus. 



In man, then, there is a small Wolffian body, early developed 

 to its full capacity, but retaining its function, as far as the glom- 

 eruli are concerned, only until the second or third month of intra- 

 uterine life, when the embryo has reached a length of 20.0 mm. 

 to 30.0 mm. In a 10.0 mm. embryo there are about thirty-four 

 active glomeruli in one organ with an average diameter of 125 

 micra; at 13.6 mm. there are about the same number, each 

 of about the same diameter, but greater efficiency is probable 

 as each glomerulus is more deeply lobed. At 30.0 mm. there is 

 still the same number. At 40.0 mm. the number of glomeruli 

 is reduced to about a dozen, and some of these show signs of 

 degeneration. 



In sharp contrast, in this respect, to the embryos of mouse, 

 rat, guinea pig, rabbit, and man are those of the pig, sheep, and 

 cat. In the pig, at 8.0 mm., there are fifty-one glomeruli on 

 one side, forty-five on the other, according to MacCallum; 

 my figures are slightly higher, fifty-four active glomeruli on each 



