Bedford, Olfactory Nerve in Sivine. 405 



of embryos of this age show that the cords are firmly attached 

 to the nasal epithelium and exhibit considerable tensile strength 

 (Fig. 12). This can hardly be accounted for unless we grant 

 that this cord is not purely cellular but somewhat fibrous in 

 character. 



Cd. 



^^:^.: 



Fig. 12. Partial dissection of the head of a I2 mm. swine embryo, show- 

 ing cords in the position of the future olfactory nerve, extending from the wall 

 of the olfactory cup toward the brain, o. c, olfactory cup; Cd., cords; A, 

 lateral view ; B, lateral-dorsal view. 



I have been unable to find, in addition to this peripheral 

 anlage, any evidence of a cerebral anlage as has been described 

 by Beard for the selachians and Chiarugi for mammals. Evi- 

 dently, at least at this stage, the development is entirely from 

 the epithelium. 



At the time of the formation of the anlage of the olfac- 

 tory nerve, the evagination of the forebrain to form the cere- 

 bral hemisphere is well under way. However, at this time, 

 there is no indication of an olfactory lobe. 



EstablisJmient of the Olfactory Ncroe. — In slightly older 

 embryos, the cord may be traced to the brain. Dissections, as 

 well as a study of .serial sections, show clearly that many sep- 

 arate cords leave the epithelium (Fig. 14). I have counted four- 

 teen on one side in one section (Fig. 1 3). These cords arise 

 from various portions of the epithelium of the olfactory region. 

 They run dorsally and slightly towards the mid-line. As they 

 approach the brain, they converge to form a cellular mass, 

 which, in later stages, appears as a kind of a cap over the end 

 of the bulbus (Fig. 13). This cap remains chiefly cellular, 

 even after the cord is almost completely fibrous. 



