INTEREELATIONS OF THE MESONEPHROS, ETC. 189 



of the anterior ones are already lost; but there is a marked in- 

 crease in lobulation and in the size of the individual glomeruli, 

 whose average diameter is now 185 micra. By 21.0 mm. the 

 organ has begun to diminish, in that there are only thirty- 

 four glomeruli on a side, with an average diameter of 200 micra; 

 and soon after this all traces of the mesonephric glomeruli have 

 vanished. 



The mesonephros of man and its degeneration have been es- 

 pecially studied by Felix in the article in the Keibel-Mall Human 

 Embryology before referred to. He shows a table of the num- 

 ber of mesonephric tubules found by him in many human em- 

 bryos up to 21.0 mm. in length, and calls attention to the con- 

 stant degeneration of the anterior tubules from 7.0 mm. on, 

 and the addition of new tubules caudally. The number of tu- 

 bules is not an absolute measure of the number of glomeruli, 

 since some of the tubules may branch, or two tubules may lead 

 from a single glomerulus; but it is sufficiently accurate for the 

 present purposes, as the irregular tubules are always few. He 

 finds an early degeneration of the organ, and then a period of 

 rest. ''From the stage of 21.0 mm. greatest length onwards, 

 all embryos show a rather constant number of mesonephric tu- 

 bules in the lumbar segments, but these tubules are almost 

 all broken in one or several places." In the quotation head- 

 ing this article he again states definitely that none of the mesone- 

 phric tubules in an embryo of 22.0 mm. greatest length were 

 capable of functioning, as in all the tubulus secretorius had sepa- 

 rated from the tubulus collectivus. In man, according to 

 Felix, the rete tubules connect only with the tubuli collectivi, 

 so that the secretory portion of all the tubules may disappear 

 before this union takes place. 



My own observations do not entirely agree with this account. 

 In a former paper I have shown rete tubules connecting with 

 the remains of the mesonephric corpuscles in certain cases, re- 

 mains which are recognizable as late as the seventh month. This 

 assures us that at least a few of the mesonephric tubules have 

 remained intact (though of course not necessarily functional) 

 from glomerulus to duct up to the time of the urogenital union. 



