342 
the cuticle lies on papilla, he will call it epithelida or epithelia, 
from émi and OA) “papille”, or “mammilla”, and he adds 
that for the same reason he calls the inside coating of the 
cheeks by the same name. (The original may be found, F. 
Ruysch, Thesaurus Anatomicus, 11. No. xxiii. p. 16, “Nulla 
subest, &c. &c. papillarum”); and again vi. No. exv. p. 49, he 
says...“Anterior pars prolabii anterioris—epithelid adhuc est 
obducta...”. 
From this it is evident that “epithelia” (changed in course 
of time into epithelium, just as platina becomes platinum) 
means ‘that which covers or is upon a papilla’, and con- 
sequently “endothelium” means that which is inside a papilla. 
The extension of the phrase epithelium to the cellular covering 
of such parts of the corium as are destitute of papille may be 
easily allowed, but it seems a daring violation of propriety to 
apply the phrase “within the papilla” to the cells coating sur- 
faces of which one great characteristic is that they are devoid of 
papilla! There seems to be something attractive about “thelium” 
that tempts writers to make use of it. Already “endothelium” 
has given rise to “ectothelium”, and probably “thelium” will 
soon become a kind of histological maid-of-all-work, with as 
many prefixes as there are kinds of cells. | 
Inthe second place, there are objections to the use of the 
term endothelium not etymological in their nature. Without 
considering the peculiar views of His on the connective tissues 
of the body, it still seems desirable to have some distinctive term 
to denote the epithelium which is formed out of the elements of 
the middle of the three layers of the germ (the mesoblast of 
Mr Huxley and myself), the word epithelium being reserved for 
the nether layer (or hypoblast). If so the word endothelium 
cannot be employed with this meaning, for it would then in- 
clude structures still called epithelium, and differing in no 
essential characters from the epithelium derived directly from 
the hypoblast. 
