410 PROF. G. ELLIOT .s^riTll OX THE 



In the intevpretatioii of the morphology of sulci, one is not disposed to place any gi-eat 

 reliance upon physiological evidence ; i'or, even supposing that the functions of the 

 various regions were knowii, it does not necessarily follow that homologous areas are 

 homodynamic in ditferent Orders. Nevertheless it is of interest to note how fully 

 the results of physiological research support the view that the u})per part of the Sylvian 

 fissvu-e represents the suprasylvian sulcus. 



Thus Terrier records * that stimulation of the dorsal lip of the suprasylvian sulcus in 

 the Cat causes retraction of the angle of the mouth and movement of the eyes to the 

 opposite side, Avhereas pricking or sudden retraction of the opposite ear is the result 

 of applying the electrodes to the lower lip of the suprasylvian sulcus. Stimulation of tlu' 

 corresponding tips of the upper part of the Sijti-ian fssiire in a moiikeii (Macacus) 

 produced ilie same results as that elicited by exoitatian of the lips of the suprasijloia ii 

 sulcus in the Cat (tig. 335). The results obtained by Ferrier in the case of Lepus (p. 73 i) 

 are in full accord. 



In Edinger's summary of the results of physiological experiment on the cerebral cortex 

 he represents tv.'O diagrams-!, horrowed from Gustav Mann, showing the lateral aspect of 

 the brains of the Cat and Rabbit respectively : in these the suprasylvian sulcus is repre- 

 sented seimrating two areas labelled respectively "Oculomotor" [the dorsal] and " Auris " 

 [the ventral]. Edinger inserts a diagram of the human brain alongside these, and labels 

 the dorsal lip of the posterior end of the Sylvian lissure " Ocnlomot." and the ventral lip 

 " Auditus.'' 



Now, as it would be absurd to imagine that the results adopted by Eerrier, Schafer, 

 Mann, and Edinger Avere in any Avay biassed by such a (to tliem) rank heresy as the 

 belief in the identity of the Sylvian and supi'asylviau sulci, the evidence which they 

 unconsciously produce is of value as an indication that one who entertains such a belief 

 cannot he accused of flagrantly disregarding physiological data. Moreover, this wholly 

 unexpected support from ihe i^hysiologists is the last link in a long cliain of irrefutable 

 evidence (only a feAV links of which have been incorporated in these notcsj that the upper 

 [caudal] part of tlie Sylvian lissure of the Primates and the dorsal limiting sulcus of Reil 

 (the " opercular " sulcus of Marchand) represent the supi-asylvian sulcus of quadrupeds. 



The stable suprasylvian sulcus, by its " union " with that variable suprarhinal kink 

 which I have called " pseudosylvian sulcus," gives a fixity to the latter Avhich it did not 

 possess l)efore ; and the result is the Sylvian fissure, or, to be strictly accurate, part of the 

 postericn- limb of the tissura Sylvii. 



In the ijeneral review of the condition of the sulci in the Mammalia, it Avas noted that 

 in the Eodent Dolichotis and in the Edentate 3Ii/rmecophaga a peculiar union of the 

 suprasylvian and pseudosylvian sulci occurs. In the light of the foregoing discussion, 

 thc^'.e facts may be simply expressed by the statement that these two mammals have a 

 Prosiniian Sylvian tissiu'c. 



If, alter cai-efully studying the arrangement of the sulci in the ^Eluroid and Cynoid 



* E. .\. Scliiifpr, ' Text-ISook of Physiology," voL ii. liiUd, fig. :3;!3, p. 7;i4, fig. S.'So, p. 735. 

 -j- •• TUr Anatomy of the Central Xervous Sy^tcm," Aun'iican traiisUitioii, l^US.1, p. l?2.j. 



