284 Journal of Comparative Neurology. 



cry. In order to do justice to the occasional origin of an axone 

 from a dendrite instead of from the cell-body, and also to the 

 peculiarity of the segmental afferent neurone, Cajal has, in his 

 new work* maintained three 'laws ' established by him: 



1. The law of economy of time. In the spinal ganglia 

 the cells are attached to the fibers so as to form a T. The con- 

 ductors are thereby placed into the very axis of the ganglion 

 and in the direction of the shortest way between periphery and 

 posterior root ; and the current need not pass through the ex- 

 centric cell. 



2. The law of economy of matter. In the midbrain of 

 fish, batrachians, reptiles, and birds, there are certain fusiform 

 cells, the axone of which originates from a dendrite. In this 

 way the axone spares the whole distance between the cell-body 

 and the point of the dendrite from which it originates. 



3. The law of economy of space. The body, i. e. the 

 most voluminous part, of certain neurones is (occasionally) 

 placed in regions poor in dendrites or final arborizations of ax- 

 ones, for instance Dogiel's cells of the internal granular layers 

 of the cortex. 



' On careful consideration of the physiological meaning of 

 the cell-body, one comes to the conviction that it presents noth- 

 ing but the convergence of the protoplasmic expansion towards 

 the origin of the axone, enlarged by the presence of the nu- 

 cleus.' He adds in a note: 'The cell-body is after all only a 

 segment of the conductor.' 



We need not comment on these exaggerations of 'legisla- 

 tive tendency,' but refer to what was said of the efforts of van 

 Gehuchteti towards making the segmental afferent neurones ap- 

 pear lawful (see p. 266). 



Berkley has probably been most explicit concerning the 

 mode of contact between cell-elements, in the Johns Hopkins 

 Hospital Reports, Vol. VI, p. 89-93 and plate XV (the intra- 

 cerebral nerve-fiber terminal-apparatus and modes of transmis- 



1 S. Kam6n y Cajal. El sistema nervioso del Hombre y de los Vertebrados, 

 I fasc. Madrid, 1897. 



