MORPHOLOGY OF THE HUMAN URINOGEXITAL TRACT. 331 



- VII. The Eelation of the Views advanced to certain 

 Developmental Arrests. 

 VIII. On the Nature and Development of Mucous 

 Membranes. 

 IX. Summary. 



I have to explain that the greater part of the work was done 

 in the Laboratory of the Eoyal College of Physicians, Edinburgh. 

 Most of the microscopical specimens and of the microphoto- 

 graphs were made by Mr J. Hume Paterson, and those of the 

 early chick by Mr Eichard Muir. The incubation of the chick 

 embryos was under the charge of my late assistant, Dr Allan 

 Brough, and was carried out at the Laboratory of the Eoyal 

 College of Physicians. Some of the work was carried out in my 

 practical room. Surgeons' Hall. The clinical casts were made 

 by myself on suitable cases prior to operation. To the Labora- 

 tory Committee, and to all the workers mentioned above, I have 

 to express my great indebtedness. 



I have also to state that the University of Edinburgh gave 

 me a most generous grant from the Moray Fund towards the 

 considerable expense involved in the work done, and also an 

 additional grant for the plates of this paper, and I beg to tender 

 my hearty thanks for their munificence. 



I must now finally enumerate the material used in this in- 

 vestigation. It divides itself into (a) that of the human foetus, 

 and (b) the adult specimens and foetuses of lower mammals. 



(a) 1. Human embryos, 3 mm. and 4 mm. in serial sections. 



2. Human embryo, serial sections, 28th day. 



3. Pelvis of human embryo, serial sections, 6th and 7tb 



week. 



4. Pelves (central slabs) of human female foetuses at 14th 



and 28th week, serial sections. 



5. Male foetuses at 8th week, 12th week, 14th week, and 



18th week (central slabs, serial sections). 



6. Prostate and adjacent parts in full-time male foetus 



(serial sections). 

 These were the successful specimens. As all embryologists 

 know in regard to early human foetuses, the tissues are often 

 not fresh enough for exact microscopical work, and I have had 



