503 ANATOMICAL TECHNOLOGY. 



(8) Continuity of the rhinalia with the postrMnalis ; of the Sylman with the point of 

 their junction ; of the superorbitaJ, with the rhinalis ; of the ealloaal with the hypoeampal, 

 and with the prmradicalia when present. 



§ 1367. Variable Characters. — (1) More or less frequent presence of the following ten 

 inconstant fissures : confinis, falcialis, intermedia, lunata, medilateralis, postcnieiata, post- 

 marginalis, postradicalis, prwradicalis, aubfaldalis. 



(2) Frequent union of the aiiaata with the coronalis and lateralis ; of the lateralis with 

 the anaata mid- medilateralis; of the diagonalis vn.t\i the anterior; of the supersylman 

 and postica ; of the ma/rginalis with the poatmarginalis. 



(3) Occasional unions of the medilateralis and confinis ; of the criiciata and the aple- 

 nialis. 



(4) Very rare unions of the postica and the rhinalia ; of the anterior with the super- 

 aylvian. 



§ 1368. Homology of the Human and Feline Fissures. — The determination of the 

 identity of the human fissures with those of the other Mammalia has long been desired from 

 the standpoint of Comparative Morphology and Systematic Zoology. Eeferring in 1868 to 

 his Lectures on the Brain in 1843, Owen says (A, III, 116) : " The main object which I 

 had in view was the determination of the homologous and superadded convolutions in the 

 more complex prosencephalon of man." 



Since the discovery in 1870 by Fritsch and Hitzig (1) of the electrical excitability of 

 certain areas of the cerebral cortex in the dog and cat, and the confirmation of this upon 

 monkeys by Ferrier (A, 138), there have been likewise physiological and psychological 

 reasons for the determination of these fissural homologies, and at this time probably few 

 biological events would be more generally welcomed than the presentation of incontro- 

 vertible evidence as to the human homologue of the carnivoral Fissura cruciata, or the 

 representative of the human centralis (Fissure of Rolando) in the cat and dog. 



§ 1369. The following are sufficient general examples of the diflBculties which sur- 

 round the subject and of the difierences of opinion among high authorities : — 



Gratiolet wrote (A, 10) : — 



" We need only compare the brain of an ape with that of a carnivore or a ruminant to 

 see that the convolutions present very dissimilar general arrangements in the several 

 orders of Mammalia. These diilerences are so great that it would be imprudent to estab- 

 lish corresponding subdivisions and to investigate their homologies. In fact, this ques- 

 tion has as yet no basis of certainty, and we think that for the present It should not be 

 undertaken." 



Owen says (i25) that the same names apply to the fissures of the Aye-aye and the cat, 

 while the very next paper in the volume of the Zoological Transactions contains the 

 admission of Flower (6) that, as between the Lemurs and the Carnivora, the " nomencla- 

 ture utterly fails." 



§ 1370. Special examples of the diversity of opinion are furnished by the two fissures 

 already named, the criieiata or " frontal " of the cat and dog and the centralia of man. 



The centralis is homologized with the auperorUtnlis bv Duval and Keller (A, 57, note), 

 and apparently by Broca ; Hitzig (A, 136, 137, Fig. 10, 11) makes it equivalent to the 

 anaata together with a part of the supersyloiana, a view which derives some support from 

 the occasional interruption of the human centralis ; it is the homologue of the coronalis 

 in the opinion of Owen (A, III, 130), Meynert (1), and Pansch (1, 47). In an earlier 

 paper, however, Pansch regarded the centralis as homologous with the crudata, and 

 this is the opinion of Ferrier and Clevenger. 



The cruciate fissure of the Carnivora is said by Ferrier (A, 199) to be experimentally 

 the equivalent of the centralis, and Clevenger (2, 14) states that the two fissures are " his- 



