Obersteiner, The Structure of the Nervous System. 83 



the cells of Clarke's columns, from which again arise the fibres 

 of the lateral cerebellar tracts ; many collaterals of the fibres of 

 the posterior roots pass through into the anterior horns here to 

 subdivide; still others cross the middle line in the posterior 

 commissure, etc. 



Lenhossek (Anat. Anz., 1800) and Ramon y Cajal describe 

 also fibres of the posterior roots which spring from lateral cejls 

 of the anterior horn and, accordingly, merely pass through the 

 spinal ganglion without coming into direct connection with its 

 cells. Whether these fibres, which Edinger, Waldeyer, and 

 others follow from the posterior horn through the anterior com- 

 missure into the decussating anterior bundles, are direct })rocess- 

 es of the posterior roots or their collaterals, cannot be definitely 

 decided. 



When we inquire for the physiological application of the 

 newly acquired anatomical knowledge of the spiral cord, we 

 must first admit that it teaches us very little about the path of 

 conscious sensations. Apparently the ascending longitudinal 

 branches of the fibres of the posterior roots, for the most part, 

 pass on into the medulla oblongata and here enter into physio- 

 logical connection with certain cells (e. g. nucleus gracilis and 

 nucleus cuneatus) wliich then by means of their axis-cylinder 

 processes (as, for example, in the fillet ) effect tlie connection 

 with the cerebrum. 



The simplest reflex loop is from the terminal brush of a 

 sensory collateral in the anterior horn to a motor cell, from the 

 latter of which the fibre of the motor root springs. The basis 

 for more extended reflexes may be found in the fact that every 

 longitudinal sensory fibre of the spinal cord sends a great num- 

 ber of collaterals into the gray substance of the cord. 



With reference to the other parts of the central nervous sys- 

 tem, especially the cortex of the cerebrum and of the cerebel- 

 lum, the investigations of recent years has furnished an abun- 

 dance of new knowledge. We cannot, however, enter into the 

 subject here without widely trangressing our limits. 



It was our purpose in writing these lines to give merely a 

 general account and criticism of the most recent results in this 

 field and to make plain how much our anatomical and physio 

 logcal funidamental ideas must be modified by reason of them. 



