MORPHOLOGY OF THE CEREBRAL CONVOLUTIONS. 311 



and separate character can be better discerned and studied in the negro, where it 

 will be found much freer from secondary and tertiary markings, approaching in 

 this respect more nearly the conditions as found in the monkeys and apes, than in 

 the white brain. If it should be considered necessary to divide it into two por- 

 tions under distinct names for purposes of description and localization, then these 

 two divisions should be considered in their proper light; that is, merely as separa- 

 tions of the tj'pical convolution, P 2 P2 1 . and not as distinct and separate convolu- 

 tions comparable with the others. 



The fissure i p, interparietal, separating the convolutions, P 1 from P 2 , was 

 first recognized and described as typical by Turner, 1 who gave to it the name of 

 fissura interparietalis. It has been recognized as typical by Pansch, Ecker and 

 other more recent writers. It has been due to the non-recognition of the typical 

 nature of this fissure by many writers that much of the confusion respecting this 

 lobe, referred to above, has arisen. Bischoff admits that this fissure is present in the 

 foetus, and typical, but he does not agree with Turner as regards its nature in the 

 adult brain. He remarks in his paper, 2 " according to my observations, although 

 it arises in the foetus a typical furrow, it is, as I believe I can demonstrate, misun- 

 derstood by Turner, and is not present in the adult in the manner described b}- 

 him." He does not state, however, how he found it, nor in what the difference 

 consists. All the more recent writers have, however, admitted the existence and 

 typical nature of this furrow. It is true that it is usually bridged over in one 

 place, sometimes in two, but this is no reason for rejecting its typical nature, lor 

 the frontals are constantly bridged and even the calcarine and central have been 

 found so. It appears, therefore, to be in every respect typical in its character. In 

 the Simiadse its important nature is very evident, see figures of Plates XXXVII 

 and XXXVIII, where it will be found as one of the best marked furrows of the 

 lateral surface of the hemisphere. In the negro brain this fissure is much more 

 simple in its nature and better defined than in the white brain. Indeed, in the 

 negro brain it is a deeply marked and but slightly tortuous fissure, often com- 

 pletely unbridged and approaching very closely the condition as found in the 

 higher Simiadse, such as the Chimpanzee, Plate XXXVIII, fig. 13 and Plate 

 XXXIX, fig. 4. In the posterior view of the occipital lobe of the negro, Plate 

 XXXVI, fig. 5, the posterior portion of this fissure will be seen, the anterior por- 

 tion of which is so well marked in Plate XLII, fig. 1. In this brain the whole 

 extent of the fissure is only interrupted by the small annectant or bridging gyrus 

 marked x, corresponding in this respect to the condition as found in the left hemis- 

 phere of the Chimpanzee, Plate XXXVIII, fig. 18. and Plate XXXIX. fig. 4. This 

 was also the case in many other negro brains examined, whilst in some, as is seen 

 in that of a mulatto, Plate XXXVI, fig. 6, and Plate XLIV, fig. 1. it is found to 

 be entirely uninterrupted throughout its whole extent. Its sides are, however, 



1 Edinburgh Medical Journal, 1866. 



2 Die Grosshirnwindungen des Menschen, etc. 



39 JOURN. A. N. S. PHILA., VOL. X. 



