430 PROCEEDINGS OF THE ACADEMY OP [1879. 



appearance of these arches is not always easily discerned. He also 

 distinguishes a superior internal (obere innere oder vierte Scheitel- 

 bogenwindung) surrounding the upper extremity of the fissura per- 

 pendicularis interna. This corresponds with the pli de passage 

 superieur externe, Gratiolet, gyrus occipitalis primus, Ecker ; 

 oberer Zug der^iintern Central windung (in part), Huschke ; erste 

 obere Hinterlappenwindung, Wagner, first external annectent gy- 

 rus, Huxley; first bridging annectent or connecting g\~rus, Turner. 

 An inferior internal (untere innere oder fiinfte, Scheitelbogenwin- 

 dung) surrounding the lower extremity of the fissura perpendicu- 

 laris interna. This corresponds with the pli de passage interne 

 inferieur of Gratiolet; gyrus cunei of Ecker. The existence of a 

 pli de passage interne superieur is not admitted by Bischoff, who 

 considers that this convolution is homologous with the pli de pas- 

 sage superieur externe. Ecker dissents from this vievv of the 

 case, and the speaker had attempted to show in a previous com- 

 munication (Plis de passage in the Primates, Proc Acad. Nat. 

 Sciences, Philadelphia, 1878) that at least in certain cases Bischoff 

 is correct. In the occipital lobe Bischoff distinguishes three con- 

 volution groups, an outer upper, the so-called ounus, and two 

 lower, an internal superior (lobulus lingualis), and an external in- 

 ferior (lobulus fusiformis). In the temporal lobe Bischoff" does 

 not differ in his divisions from previous writers. 



The observations referred to at the beo-inninor of this communi- 

 cation in reference to the union of the central and Sylvian fissures 

 is not in accordance with the views of Bischoff, at least in the ab- 

 solute manner in which he proposes them ; and that he considers 

 the presence of these arching convolutions around the ends of the 

 primary furrows as absolutely essential, is shown by his criticism 

 of Turner's observation referred to above, and also of Dr. Rol- 

 leston's observations on the premier pli de passage. In seven 

 human brains examined by Dr. Rolleston in reference to the de- 

 velopment and character of this convolution, he found it in one 

 case entirely wanting on one side. Bischoff regards this as an 

 error, stating that this is a very typical and characteristic convo- 

 lution, which, according to his view can never and will never be 

 found wanting where deep and extensive anomalies in brain de- 

 velopment have not taken place. 



In conclusion, he could but repeat the opinion of Ecker, "what 

 Bischoff says is also perfectly correct, that a large number of the 

 convolutions of the cerebral hemisphere are arranged around the 

 ends of the primary furrows in more or less simple or compli- 

 cated arches; and it cannot be otherwise, for the ranges of moun- 

 tains inclosing a valley must necessarily pass into each other 

 where the valley ends, but no special explanation seems to be 

 thereby disclosed." 



