[Proc. Roy. Soc. Victoria, 24 (N.S.), Pt- I, 1911. 



Art. XI. — Subdivision of the Sinned Canal in the Lxvruhar 

 Region of Chick Embryos. 



By HELEN KEL8EY. 



(With Plate X LI r.) 

 [Read 13th July, 1911.] 



While examining serial sections of a chick embryo of about 

 fifty-two hours' incubation, it was noticed that at the posterior 

 end of the cord, in what would be the lumbar region of the 

 adult, the central canal of the spinal cord was distinctly sub- 

 divided. At first this was regarded as an individual abnormality, 

 but since then a large number of specimens have been examined, 

 and the division has been found to occur* invariably at a certain 

 stage in the development of the embrj^o. 



All the specimens were preserved in picro-sulphuric acid, 

 subsequently stained with acetic acid, alum and carmine, and cut 

 serially. The eggs used for incubation were procured from a 

 number of different hens, and were incubated and examined 

 during the springtime of three successive years, so that there is 

 no reason to doubt that the development is normal. 



Previous observers have described multiple canals and branch- 

 ings of the central canal of the spinal cord in the chick (see 

 Bibliography), but these are evidently different in nature from 

 those now dealt with. In all cases they have been regarded as 

 individual abnormalities and not, as certainly appears to be. the 

 case, as indicating a normal stage in the development of the 

 spinal cord. 



Then again, they occur at a much later date, when those now 

 dealt with have completely disappeared. Miss A. Smith (1899), 

 for example, describes them in a. chick of 10 days' incubation, 

 and as occurring far forward at the level of the heart and lungs. 

 Federow (1907) descrilies them in a 5-6 days' chick. 



In all those that I have examined, the maximum development 

 occurs between the fifty-second and fifty-sixth hours. Tlie period 

 ^f subdivision extends from 48 to 58 hours' incubation. 



