34 STUDIES ON THE CENTEAL NERVOUS SYSTEM 



A real frontal trigeminal nucleus is present in amphibians 

 and in reptiles, in birds and in all mammals. Figure 7 

 gives a scheme of the relations in the fifth nerve. In the 

 old systems (black in this diagram) the reflex stimuli and 

 the stimuli for pain, heat and a part of touch are conducted 

 (palaeosensibility). In the younger systems (dotted in this 

 diagram) the chief part of touch, and the pathways for 

 deep sensation and tactile discrimination are localised. 



Investigations, made in cooperation with Dr. Zeehande- 

 laar, showed that in the human development the same 

 relation exists, at least in regard to the spinal cord. In the 

 human foetus of 5 centimeters, for example, the posterior 

 columns are still very small. They grow gradually in older 

 foetera and in children and in this way we see that onto- 

 genetic development runs parallel with the phylogenetic. 



Looking over the results, thus far obtained, we may de- 

 duce the following points. Clinical investigations teach 

 that a higher form of sensibility must be led by the posterior 

 columns, the more primitive one by the lateral columns. 

 The study in comparative anatomy shows that the oldest 

 form of sensibility must be localised in the antero-lateral 

 tracts, the newer form in the posterior columns. Hence 

 it seems correct to accept the conclusion that this neosensi- 

 bility corresponds with the above mentioned higher form of 

 sensibility. 



More recent investigations, however, have shown that the 

 palaeosensibility does not remain the same during evolution. 

 Just as is so often seen in the central nervous system the old 

 parts develop further and are more finely organised in higher 

 animals and in man. This is also the case in the primary 

 fields of sensibility. The posterior horn of the spinal cord in 

 reptiles and in birds is of a much simpler build than in man, 

 and, the substantia gelatinosa Rolandi, for instance, is not 

 present there. This part of the posterior horn develops in 

 mammals and interesting investigations by Ariens Kappers 

 have shown that mammals with a rich development of 



