62 Journal of Comparative Neurology. 



the rabbit there also existed an extremely small layer of nerve 

 cells, connecting both hemispheres, representing extensions of 

 the cortex over the callosum. Blumenau finds the free dorsal 

 surface of the rabbit's callosum very small and covered with a 

 thin and scarcely noticeable layer of cinerea. The same writer 

 finds the indusium well developed in the pig. The striae later- 

 ales are large, but caudad they recede from the meson and flat- 

 ten out; between these strise there is a minimum layer of cin- 

 erea. 



Giacomini'' has also noted that the elements of the brain 

 cortex enclose these striae, and that a thin intermediate layer of 

 cinerea exists. This he differentiates into two layers: A su- 

 perficial (continuation of the molecular stratum), and a deep layer 

 containing scattered nerve cells with many processes, which con- 

 firms his opinion that the dorsum of the callosum is covered by 

 a thin 'but unfailing layer. 



Wilder,'' states that he observed the continuity of the 

 cinerea upon the human callosum, in 1880; he adopts Ober- 

 teiner's term indusium, dropping the adjective ^mr/^;;/.* 



The intimate relationship existing between the indusium 

 and the callosum during development, renders necessary a de- 

 scription of the changes undergone by the callosum. March- 

 and's^ paper, with the beautiful figures accompanying it, has 

 given, in its representation of the different stages, quite a com- 

 plete series from the proton f or beginning of the combined 

 callosum, fornix, precommissure and hemiseptum, to the con- 

 ditions found in the adult. This proton appears first as a thick- 

 ening in the terma. There is formed at this time, or a little 

 previously, along the mesal aspect of each hemicerebrum, a fur- 



* Since the nonn indusium is employed in several senses, and is, there- 

 fore, what Wilder has termed (i6, g 23) a polychrestic word, its special 

 application should be indicated in the title of a paper, or when first used in a 

 paper, by a qualifying word or phrase, e. g., callosale, callosi, of the callosum, or 

 griseum . 



t A term suggested by Wilder (7, ^46), '• to designate the primitive, undif- 

 ferentiated mass or rudiment of a part;" it is the equivalent of the words Anlage 

 s^nd fundament &s employed by Minot'' and Mark, respectively. 



