26o 



NERVOUS SYSTEM OF VERTEBRATES. 



medial lemniscus in mammals should stop in the corpora quad- 

 rigemina. The large branch of the medial lemniscus which runs 

 to the anterior quadrigemina may be made up of such fibers. 

 The structure of the corpora quadrigemina is shown in Figures 

 129 and 130. 

 The lemniscus system in lower vertebrates is related to an 



Fig. 130. — Transverse section of the anterior corpus quadrigeminum of the 

 rabbit of eight days. From Cajal (Beitrage u.s.w.). A, surface at the median 

 line; B, superiicial gray layer; C, layer of opticus fibers; D, transverse fiber layer; 

 a, border cells; b and c, horizontal spindle cells; e, vertical spindle cells; /, g, various 

 cell types of the gray layer; h, j, spindle cells of the opticus layer; M, L, cells of 

 the fiber layer; n, ending of opticus fiber. 



indifferent tectum mesencephali. It has been differentiated into 

 a medial general cutaneous tract and a lateral auditory tract. 

 The auditory tract has claimed the caudal portion of the tectal 

 region. The cutaneous tract, while it is probably related to the 



