NATURE OF SENSE ORGANS 



29 



olfactory cell with the olfactory nerve-fiber was first seen 

 by Babuchin in 1872 who showed that in a gold-chloride 

 preparation, fibers could be traced from the nerve to the 

 cells that were suspected by Schultze to be sense cells. 

 In 1886 this connection was demonstrated with much 

 greater certainty in methylen-blue preparations by 

 Ehrlich whose results were con- 

 firmed the following year 

 by Arnstein. 



Because of the transitoriness 



of methylen-blue preparations, 

 the results of Ehrlich and of 



Arnstein were looked on with 



some suspicion till they were 



reproduced in Golgi preparations 



by a number of workers, such as 



Grassi and Castronovo (1889) 



on the dog, Ramon y Cajal (1890) 



on mammal embryos, Van 



Gehuchten (1890) on rabbits, von 



Brunn (1892) on man, Retzius 



(1892a, 1892b, 1894) on fishes, 



amphibians, reptiles, and mam- 

 mals, and by many other later 



workers on various vertebrates. 



( Fig. 6 ) . The results of all recent 



students in this field of histology 



support the statement that the 



olfactory epithelium of vertebrates is composed of at 



least three classes of cells : basal cells, ordinary epithelial 



or substentacular cells, and sense cells from which the 



olfactory fibers take their origin. Thus the opinion of 



Fio. 5. Olfactory epith- 

 elium from a pig embryo 

 6J4 inches long; b, basal 

 cell; 0, olfactory cell; s, sus- 

 tentacular cell. After 

 Alcock, 1910, Fig. 10. 



