66 Journal of Comparative Neurology. 



vidual difference rather than the rule, as I liave examined sev- 

 eral brains of this age and have not seen one closed or 

 nearly so. 



Broca in 1888 (4^ 545) said: "This superficial position of the 

 cephalic extremity of the insula has been observed, more or 

 less, in man, upon a great number of new-born children or 

 those of a few months old ; after the second year it is rarely 

 seen except upon the brains of idiots and imbeciles (and also in 

 some deaf-mutes)." 



The determination of the exact time of closing of the Syl- 

 vian fissure in the normal human brain is of considerable mor- 

 phologic importance as it marks the completion of a period 

 of remarkable growth of these lobes ; and in making a collec- 

 tion of brains between the eighth and twelfth months for this 

 purpose as many as possible should be obtained so that individ- 

 ual differences might not induce a wrong conclusion. 



The operculums do not always completely close the Sylvian 

 fissure and hence the insula is exposed sometimes even- in the 

 adult human brain. In 1887 Rolleston (49^ 35), in his descrip- 

 tion of an adult male Australian brain, said: "The island of 

 Reil is exposed on the left side. . . The exposure of the 

 island of Reil implies that the surrounding gyri are ill-devel- 

 oped; Broca's convolution is thus shown to be defective, a point 

 of interest in an Australian savage whose language is primitive 

 as shown by its unclassified character." It is questionable if 

 facts would bear out this conclusion, and while some of the gyres 

 might in this specimen have been "ill-developed" it would 

 have been interesting to learn if this had been observed on 

 any other specimen. 



The brain of the philosopher Chauncey Wright has a part 

 of the insula exposed. In 1889 Wilder (g3,i 58) said : " Whether 

 any of this condition is due to pressure during hardening 

 which may have occasioned also the peculiar roundness of the 

 temporal lobe, it is impossible to determine and Dr. Dwight 

 does not recall the condition of the parts when the brain 

 was removed." In others, as that of the Swedish carpenter 

 (No. 318), the operculums not only conceal the insula but abso- 



