1892.] NATURAL SCIENCES OF PHILADELPHIA. 207 



primates, if correct, has a physiological as well as a morphological 

 significance when considered in connection with the localization by 

 Broca and other observers of the centre of articulate language in the 

 inferior or third frontal convolution. For if the centre of speech be 

 localized in that convolution, in its absence, though the larynx and 

 nerves involved be present, the nervous plexus being inconiplete, 

 speech becomes impossible. The parietal lobe anteriorly is separated 

 from the frontal lobe by the central fissure, posteriorly from the 

 occipital by the external and internal occipital fissures and laterally 

 and inferiorly, at least in great part, from the temporal lobe by the 

 posterior branch of the Sylvian fissure. The posterior central con- 

 volution, the most anterior portion of the parietal lobe, may be 

 regarded as giving origin to the superior and inferior parietal 

 lobules which, passing backward towards the occipital lobe, are 

 separated by the parietal fissure, PI. XI, fig. 2. 



The parietal fissure begins above and a little beyond the middle 

 of the posterior branch of the Sylvian fissure and passes upward 

 and forward, then obliquely upward and backward, and having 

 nearly reached the top of the hemisphere turns again and finally 

 passes into the external occipital fissure. Of the three secondary 

 fissures of the superior parietal lobule, the most noticeable is that 

 upon the surface of the hemisphere, just posterior to the central 

 fissure which resembles very much in its form the cruciform 

 fissure of the orbital surface of the frontal lobe. Of the convolu- 

 tions entering into the formation of the inferior parietal lobule we 

 regard those surrounding the terminations of the Sylvian and 

 superior temporal fissures as being the supramarginal and angular 

 convolutions. 



The mesial surface of the parietal lobe of our Gorilla was not as 

 well preserved as the remaining parts of the brain, nevertheless that 

 part of it lying between the ascending branch of the calloso-marginal 

 and internal occipital fissures was identified as precuneus. The occip- 

 ital lobe, forming the posterior portion of the hemisphere, is separated 

 from the parietal lobe raesially and internally by the internal occipital 

 fissure, and externally and laterally by the external occipital fissure. 

 There are, however, no distinct boundaries between the occipital lobe 

 laterally and inferiorly and the parietal and temporal lobes, the 

 occipital passing continuously into the latter lobes as the occipital 

 and occipito-temporal convolutions. The internal and external 

 occipital fissures in the brain of the Gorilla mig'ht be viewed when 



