284 NERVOUS SYSTEM. 



least in this portion of the cord. 1 Recent experiments upon 

 the cervical portions of the cord show that there is a very 

 slight decussation of motor fibres in this situation. The first 

 observations pointing to this conclusion are those of Brown- 

 Sequard. " There is always, even in mammals, after a trans- 

 versal section of the whole or a lateral half of the spinal cord, 

 at least some appearance of voluntary movements in the side 

 of the injury, and always also a diminution of voluntary move- 

 ments in the opposite side ; so that, in animals, there seems 

 to be in the spinal cord a decussation of a few of the volun- 

 tary motor conductors. As there seems to be no such decus- 

 sation in man, at least according to several pathological facts, 

 we shall not insist upon its existence in animals." 2 



Yan Kempen has repeated and extended the very re- 

 markable experiment of Galen, with the most satisfactory 

 rosults. This observer made a median, longitudinal section 

 of the cord in dogs and rabbits, at the site of the fifth, sixth, 

 and seventh cervical vertebrae. " This experiment was fol- 

 lowed by partial paralysis of voluntary movements in the 

 posterior extremities, so that the animal thus operated upon 

 moved the posterior limbs and was able to change his posi- 

 tion, without, however, being able to raise himself." 3 



As there is some difference in the results of observations 

 upon different animals, and as decussating motor fibres have 

 never been demonstrated in man, it is impossible to apply 

 the above experiments without reserve to the human sub- 

 ject ; but they show, nevertheless, that, in mammals, the 

 motor columns of the cord probably do not decussate in the 



1 GALENUS, De Anatomicis Administrationibm, Liber viii., Cap. vi. Opera 

 omnia, Lipsiae, 1821, tomus ii., p. 683. 



These remarkable experiments must have been made in the latter half of the 

 second century, as Galen was born in 131, and died about the year 200. 



2 BROWN-SEQUARD, Physiclogy and Pathology of the Central Nervous System, 

 Philadelphia, 1860 ? p. 48. 



8 VAN KEMPEN, Experiences physiologiques sur la transmission de la semibilite 

 et du mouvement dans la moelle epinere. Journa 7 de la physiologic, Paris, 1 859, 

 tome ii., p. 528. 



