Meyer, Data of Modem Neurology. I2i 



splendid illustrations of the principal points just set forth. We 

 shall refer to them in full. 



Wilhelm His arrived at similar conclusions on ground of 

 embryological observations and considerations. I mention here 

 a summary of propositions which the famous embryologist 

 communicated to the Anat. Gesellschaft. ^ 



1. There is a period in the embryonic life in which no 

 nerve fibers exist, neither central nor peripheral ones. 



2. The motor nerves originate as processes of definite 

 cells of the spinal cord and brain. 



3. The axis-cylinder processes appear as the first pro- 

 cesses of the motor cells ; the ramified (protoplasmic) processes 

 are formed considerably later. 



4. The motor cells show early a fibrillary cell-body and 

 the fibrillation is continued into the relatively broad axis- 

 cylinder. 



5. The motor cells, both of the spinal cord and brain are 

 located in definite and constant zones of the medullary tube 

 (brain-axis and spinal cord). The latter consist of a floor-plate 

 and roof-plate which connect the lateral walls in the median 

 line. The lateral wall again is divided into a dorso-lateral (alar) 

 and a ventro-lateral (basal) part. 



6. All motor nerve-roots originate from cells of the ven- 

 tro-lateral (basal) part of the tube; but not all the cells of that 

 part send their axis-cylinder into the motor roots. A few of 

 them grow towards the anterior commissure and others seem to 

 enter into the formation of the longitudinal tracts of the cord 

 and brain. 



7. The motor nerve-fibers leave the tube in several types 

 (See the copy of the drawing of His, Fig. 4): A. The type 

 of the motor spinal roots and of the 12th, 6th and 3rd cranial 

 nerves. B. The type of the spinal accessory and the motor 

 divisions of the pneumogastric, glossopharyngeal and 5th. — 

 origin from a lateral nucleus of the 'basal plate' and exit at the 



iRerr Wilhelm His, Ueber die embryonale Entwicklung des Nervenbahnen. 

 Anat. Anzeiger, Vol. Ill, p. 449-505. 



