Kappers, Tehostean and Selachian Brain 49 



latum laterale, then bend mesad to the third ventricle (Figs. Ix, 

 Ixi), and going ventrad through the tr. thalamo-spinaHs, end 

 medially in the lobi inferiores (Figs. Ixii, Ixiii). Probably these 

 fibers include the tr. thalamo-lobaris (also called ViCQ d'Azyr's 

 bundle), as well as the tr. mesencephalo-lobaris anterior of the 

 teleosts. These fibers have been described by both Edinger 

 and Haller. 



The th alamo-spinal bundles of Galeus, already referred to, are 

 of much more importance than in the bony fishes and are also 

 rather easily follovs^ed. They arise in the so-called "centrales 

 Hohlengrau" of Edinger, or nucleus strati grisei of Houser, a 

 diffuse mass of cells situated medially to the ventricular v^alls 

 which extends backward almost in a straight line so that it lies 

 mesad to the tr. lobo-cerebellaris and immediately under and 

 adjacent to the fasciculus longitudinalis posterior. Soon after 

 their origin these fibers are joined by the tecto-spinal fibers which 

 arise farthest in front and the two tracts cannot be separately dis- 

 tinguished in their further course through the mid-brain, as their 

 fiber-caliber is the same. 



The post-infundibular tracts of selachians, which I have still 

 to describe, conform closely with the relations in the teleosts. 

 Two post-infundibular decussations have been described by 

 Edinger, one under the name, "Commissur des centralen 

 Hohlengraues," the other as "Decussatio infundibuli." In his 

 opinion the first commissure lies under and near to the ventricular 

 epithelium ventrally to the fasciculus retroflexus and its fibers go 

 to the posterior part of the 'tween-brain. As to the second decus- 

 sation he says that it consists of strongly developed but unmedul- 

 lated fibers descending from the dorsal region of the 'tween-brain 

 or from the mid-brain. After decussation these fibers go back- 

 ward into the lateral wall of the lobi inferiores, where they may 

 be followed as far as the furrows of the saccus vasculosus: "Es 

 scheint dass diese 'Tractus sacci vasculosi' sich dort aufsplit- 

 teren." A little further on he says that fibers from the "centrales 

 Hohlengrau" also decussate in the decussatio infundibuli, after 

 which they disappear in the saccus vasculosus. He again divides 

 the decussation of the substantia grisea centralis into two parts, 

 a ventral and a caudal decussation. Haller describes the com. 

 infundibularis as a connection of both the lateral post-infundib- 

 ular regions with one another. It is said that its loops reach 



