74 Journal of Comparative Neurology. 



a band of myelinic fibers, lies another cellular area called the 

 claustrum (Burdach). These fibers, says Meynert, have their 

 origin partly from the subfrontal gyre and partly from the un- 

 cus from which they radiate in a fan-shape separating the areas 

 referred to above. The same author also says (37, 674): "The 

 fibers of thQ fasciadus imcinatus traverse freely the substance of 

 the claustrum as well as that of the nucleus aniygdalcB. The an- 

 terior cord-like and hook-shaped part of the fasciculus uncinatus is 

 joined by bundles of fibers distributed, as it were, in layers 

 which pass through and along the surface of the claustrum, con- 

 stituting an important part of the medullary substance of the 

 island (of Reil) and of the external capsule." 



In 1889 Spitzka (56, 172) said the claustrum "corres- 

 ponds in extent nearly with the extent of the insula." 



Obersteiner in 1890 (42, 68) said of the claustrum, "its 

 lateral surface adapts itself to a certain extent to the cortex of 

 the island of Reil, exhibiting similar small elevations and de- 

 pressions." 



Until recently, the claustrum has been assumed to be pecu- 

 liar to the primate brain, and was an object of much specula- 

 tion; but the researches cf Betz, Meynert, Duret, Browning and 

 others seem now to prove beyond a doubt that it is really a part 

 of the insula which became separated from the cortex proper 

 by the growth of the fibers referred to above. In 1879 Richet 

 (48 23) wrote: "It appears that in the brains of idiots, the 

 white lamina, which separates the insular convolutions frorn the 

 avant-viur is absent, and the avant-mur really becomes the in- 

 ternal layer of the cortex cerebri (Betz)." The same author 

 (48 24) quoting from Duret, says the circulation is the same as 

 that of the insula. Browning in 1889 (5, 234) agreed with Duret 

 and stated that the blood supply of the claustrum passed 

 through the cortex of the insula and not through the precrib- 

 rum (anterior perforated space). This being established it would 

 seem that the presence of a claustrum was indicative of the 

 presence of an insula. It also suggests the possibility of these 

 fibers passing so far entad as not to demarcate a claustrum as is 

 probably the case in the sheep. The former inference regard- 



