Abstracted by B. F. Kingsbury, author. 

 Cornell University, Ithaca. 



The extent of the floor-plate of His and its significance. 



The summary of this paper is as follows: 1. A differentiated 

 floor-plate extends no farther cephalad than the fovea isthmi. 

 Increased morphologic significance is believed to attach to this 

 depression. 2. The plan of arrangement of the longitudinal 

 zones of His as set forth by him and generally accepted is in- 

 terpreted as giving a wrong morphologic basis for the brain. 3. 

 Theoretic considerations based partly on the 'blastopore theory' 

 indicate: a) that the floor-plate corresponds to a 'sutura neuro- 

 chordalis' (His) ; b) that the floor-plate and notochordal plate 

 are primarily coextensive; c) that the neurochordal suture does 

 not extend to the anterior end of the neural plate; d) that the 

 primary motor and sensory zones are continuous from side to 

 side cephalad of the anterior end of the floor-plate. 4. The fol- 

 lowing interpretations are accepted: a) that the optic chiasma 

 marks the anterior end of the neural plate; b) that the motor 

 zone terminates with the midbrain; c) that the floor-plate ter- 

 minates at the fovea isthmi ; d) that the boundary between motor 

 and sensory zones terminates near the mammillary recess. 5. 

 A rational basis for the division of the brain into epichordal and 

 prechordal portions is afforded by the interpretation presented. 

 6. A number of facts of cephalic and encephalic morphology may 

 be better interpreted on the basis suggested in this paper. 



