FASCICULUS CEREBRO-SPINALIS IN THE RAT 423 



does not give good results. He could follow only a few degen- 

 erating fibers into the spinal cord where they lay in the homolat- 

 eral anterior funiculus. They could not be traced beyond the 

 upper cervical segments. These findings seem to indicate a con- 

 dition in the hedgehog similar to that found by Draseke in the 

 mole. 



It would seem, therefore, that the incomplete medullation of 

 the pyramidal tract in the rat is not a characteristic peculiar to 

 these animals but is related to similar conditions in at least some 

 marsupials (pseudochirus), some species of insectivora (mole, 

 hedgehog) , some other rodents (guinea-pig) and some ungulates 

 (sheep) . Since, however, the observations on these other animals 

 were confined to myelin sheath stains it seems desirable to make 

 a comparative study of the question with an axon stain. Such 

 an investigation is now under way. 



In man, medullation of the pyramidal tracts begins shortly 

 before birth and is not completed until the second year. It is 

 obvious that this tardy medullation is rendered more significant 

 in the light of these facts concerning the condition of this tract 

 in some of the lower animals. 



BIBLIOGRAPHY 



Bechterew, W., 1890 Ueber die verschiedenen Lagen und Dimensionen der 

 Pyramidenbahnen beim Menschen und den Thieren. Neurol. Cen- 

 tralbl., Bd. 9, S. 738. 



BiscHOFF, E. 1900 Beitrag zur Anatomie des Igelgehirnes. Anat. Anz., Bd. 18, 

 p. 348. 



Draseke, J. 1904 Zur Kenntnis des Riickenmarks und der Pyramidenbahnen 

 von Talpa europaea. Monatschr. f. Psy. u. Neurol., Bd. 15, p. 401. 



Goldstein, G. 1904 Zur vergleichenden Anatomie der Pyramidenbahn. Anat. 

 Anz., Bd. 24, p. 451. 



King, Jessie L. 1910 The cortico-spinal tract of the rat. Anat. Rec, vol. 4) 

 p. 245. 



von Lenhossek, M. 1889 tJber die Pyramidenbahnen im Riichenmarke einiger 

 Siiugetiere. Anat. Anz., Bd. 4, S. 208. 



Ranson, S. W. 1912 The structure of the spinal ganglia and of the spinal nerves. 

 Jour. Comp. Neur., vol. 20, p. 159. 



