10 



ANATOMY OF THE CENTEAL NEEVOUS SYSTEM. 



months' still-born foetus. The whole of this area is, in the adult, filled with 

 nerve-fibers, which are difficult to follow because of their various directions 

 and intersections. In the section in question, however, of all the numerous 

 fibers of the cerebrum only the single tract designated the tegmental tract 

 is meduUated. In the figure the black lines locate it. At no other place in 

 the cerebrum may medullated fibers be found. Hence Flechsig was able to 

 discover, among the numerous little-known tracts of the. cerebrum, the 

 tegmental tract as a distinct one, and in part to trace its course. 



Pig. 3 rejDresents a section through the cervical portion of a spinal 

 cord from a man who lost the left forearm before birth. Note that both 

 gray and white substances — but particularly the former — are strongly atro- 

 phied on the left side. The exact determination of the extent of the 

 atrophy justifies a conclusion as to the location of the central ends of the 

 divided nerves. 



Fig. 3. — For description, see text. 



Knowledge of the general morphology of the central nervous system 

 is gained through embryology. For our knowledge of the embryology of 

 the organs we are now studying we are indebted especially to Kolliker, His, 

 Tiedemann, Reichert, v. Mihalkovics, Gotte, and KupfEer. 



As early as the seventeenth century the first attempts were made to 

 approach the brain in a comparative way; and the literature of the first 

 half of this century contains a great number of monographs on the brain 

 of the lower vertebrates. It was the fish-brain that was ever the subject 

 of renewed study. The numerous studies of this time reached a climax in 

 the work of Leuret and G-ratiolet, on "The Vertebrate Brain"; also in 

 such really great monographs as that of the Wolmar physician. Dr. Girgen- 

 sohn, on "The Brain of Fishes" (1846). Naturally all of these works are 

 concerned simply with the outer form of the brain. That is true, also, of 

 several later ones, which, undertaken from the stand-point of general 

 morphology, have given us exact knowledge regarding simply the external 



