atjT&or's abstract op this paper issueC 

 by the bibliographic service, july 12 



THE EXTENT OF THE FLOOR-PLATE OF HIS AND ITS 



SIGNIFICANCE 



B. F. KINGSBURY 



Department of Histology and Embryology, Cornell University, Ithaca, Neio York 



ELEVEN FIGURES 



In 1888 Wilhelm His first set forth his well-known interpreta- 

 tion that the neural tube consists of four fundamental longitudi- 

 nal laminae, plates, or zones — the floor-plate, the roof-plate, and 

 the lateral plates, the last being divisible into the primary sen- 

 sory zone, dorsal or alar plate, and the ventral, primarj^ motor 

 zone (basal plate) , these being demarcated from each other upon 

 the internal (ependymal) surface by a furrow, the sulcus limi- 

 tans. In the papers b}' him that appeared in 1892 upon the gen- 

 eral morphology of the brain and the divisions of the brain, and 

 in 1893 on the frontal end of the brain tube, His further applied 

 this conception to the brain. 



The importance and fundamental character of the analysis of 

 the neural tube in terms of primary longitudinal zones has been 

 generally recognized, as is evidenced from the fact that in nearly 

 every text-book having occasion to present the development of 

 the brain and spinal cord the description is largely based upon 

 the work of His and his figures are reproduced, among them one 

 or more in illustration of the longitudinal zones. 



The dorsal and ventral laminae composing the lateral walls 

 of the neural tube are the zones which by their growth furnish 

 the nervous tissue (neurones) of the brain and spinal cord, while 

 the roof-plate and floor-plate are generally interpreted as pri- 

 marily 'non-nervous,' composed of indifferent (ependymal) cells 

 alone, although this has been frequently tacitly assumed rather 

 than positively stated. Attention has thus been directed rather 

 to the lateral laminae than to the dorsal and ventral medial zones 

 that join them, which have been accordingly rather neglected. 



113 



