CHAP. XXIII.] OF THE HUMAN BRAIN. 459 



gyms has complicated connections with the adjacent convolutions 

 behind it, and receives large bands of fibres from the posterior 

 part of the hemisphere by means of the axial longitudinal system ; 

 it is also extensively connected with the anterior parietal convolu- 

 tion, and sends forwards, deeply, fibres to all the three frontal con- 

 volutions. The second frontal, besides receiving fibres from the 

 axial system and parietal convolutions, is connected with the first 

 and third frontal gyri, between which it lies, by numerous large 

 lamina, which do not simply dip transversely under the interven- 

 ing sulci, but run tortuously forwards or backwards, their inter- 

 twinings being too complicated to admit of either description or 

 representation. Fibres, moreover, cross transversely under the 

 second frontal gyrus from the first to the third." 



The convolutions of the Temporal Lobe are most distinctly con- 

 nected with others in the Occipital and in the Parietal Lobes, and 

 Broadbent adds,* it is " worthy of mention that between the infra- 

 marginal Sylvian and parallel gyri separated by the deep parallel 

 sulcus, there is the most extensive commissural connection to be 

 found between adjacent convolutions in the entire brain." Recent 

 physiological experiments, as we shall see in the next chapter, 

 render this observation one of great importance. 



The bulk of the fibres from the radiating convolutions of the 

 ' island of Reil/ form a thick layer that is in relation with the 

 convolutions into which its anterior and upper margins pass, viz.: 

 those of the posterior border of the orbital lobule, the third frontal 

 and the ascending parietal gyri. The course of these fibres is very 

 intricate. Fibres also pass between the convolutions of the ' island 

 of lleil ' and the posterior part of the hemisphere ; whilst a few 

 proceed from, or pass between, the centre of the island from the 

 overhanging tip of the Temporal Lobe. No fibres connecting these 

 convolutions with the Corpus Striatum or Thalamus have yet been 

 recognized, although they lie immediately outside the former body, 

 and may therefore receive a few filaments from its extra- ventricular 

 grey nucleus. 



From what has been said concerning the distribution of 

 the fibres of the Corpus Callosum, of the various longi- 

 tudinal sets of ' commissural fibres,' and of those which 

 pass in different directions between more or less con- 



* Loc. cit. p. 15. 



