Clark, Comparative Anatomy of the Insula. 63 



years a large number of aphasics were examined for ihe pur- 

 pose of verification, and in 1868 he published a resume of the 

 facts upon which he based his conclusion. This discovery nat- 

 urally aroused great interest in the insula inasmuch as "lesions 

 of the left subfrontal gyre generally extend into the insula," 

 while those (2 ) " confined strictly to the insula are very rare." 

 In i868Broca (4^ 1 1 3) pointed out that in aphasics there is almost 

 always a lesion in the caudal half of the subfrontal gyre of 

 either the right or the left side, and that this lesion is sometimes 

 confined exclusively to this area. However, in about one case in 

 twenty this area is apparently perfectly sound, but a lesion ex- 

 ists in the insula or an adjacent gyre with which the subfrontal 

 is continuous. The lesion is located in about 19 out of 20 

 times on the left side and the right side remains perfectly sound. 

 He had never found a case in which the patient was possessed 

 of this faculty and at the autopsy showed a lesion of both sub- 

 frontal gyres. Speech has, however, persisted in some patients 

 where an autopsy showed the total destruction of the right sub- 

 frontal. He also said he had noticed several cases of idiots who 

 had never been able to learn to read, where the subfrontal gyre 

 was absent on both sides. 



So far as the writer has been able to learn, no satisfactory 

 reason has ever been given for this strange association of the 

 subfrontal region and the insula; yet if, as Meynert (38) says, 

 " fibers from the subfrontal gyre pass just entad of the insular 

 cortex," then it would seem very likely that a diseased condi- 

 tion of those fibers sufficient to cause loss of speech would 

 affect the overlying cortex of the insula producing lesions and 

 perhaps a breaking down of the cellular cortex, as frequently 

 happens. A clot of blood, through pressure upon the insula, 

 has also been said to cause loss of speech. 



THE DEVELOPMENT OF THE OPERCULUMS. 



In 1892, Cunningham (15^ 78) said of the human brain : 

 "As Mihalkovics has pointed out, it is toward the end of the 

 second month of development that the first signs of the Sylvian 

 depression may be detected. At the same time, it is right to 



