34 



C. ir. M. Povntcr 



("•coasionallv the sulcus rotroooutralis supcriiir is iu oonmuniica- 

 tioti with the sulcus cinguli. ami more often the interior is con- 

 nected with the tlssura Sylvii; this latter continence Retzius finds 

 present iu 40 per cent., Weinberg in 44 per cent. (.\Mnnnniication 

 between the elements of the sulcus retrocentralis and the sulcus 

 centralis have already been spoken of. \\'einberg (np.O saw the 

 sulcus retrocentralis double in one case, and quotes Sernoff as 

 finding absence of this sulcus in 25 per cent.; but undoubtedly in 

 those cases belonging to Sernoff one or other of the elements were 

 present. 



The Sulcus Occipitalis Trans-irrsus (^Ecker\ rannis occipitalis 

 (^CunninghanO, has been variously interpreted as to its homologue 

 in apes and its relation to other fissure integers. \\'ilder (1885) 

 concluded that " What is commonly understood as the transverse 

 occipital of Kcker is not a fissure integer . . . the true parietal 

 and superior occipital do not form parts of one fissure, and the 

 latter is the principal and primary constituent." He (i8q6) in a 

 study of fifty-three brains finds that the sulcus occipitalis trans- 

 versns is separate from the sulcus interparietalis proprins in 13 

 per cent. Parker (1806) disagreed with \\'ilder, but considers 

 the sulcus occ. transversus a part of the interparietal, infiuenced 

 in its direction by the growth process. Spitzka (icx)i/>) elaborated 

 the theory of Parker, but attempted no proof except observations 

 on adult brains. Smith ( ux>4') considers it a part of the inter- 

 parietal integer and says. " The incisura parieto-occipitalis seems 

 to be the chief mechanical determining factor in the production of 

 this in the human brain." 



Regio Occipitalis 

 The greatest advance in the attempt to interpret the fissures of 

 the cranium is undoubtedly the memoir of Smith (1904) on this 

 region. Instead of attempting to homologize fissures by position 

 when we have no constant landmark to reckon from, he makes a 

 radical departure from old methods and studies the fissures in 

 their relation to histological-physiological areas. Such a method 

 is in keeping with other present neurological work, and as other 

 regions become known physiologically, the whole cerebral mor- 



