893 DR. CAVAFY. 



admitted to be mistaken, and he has completely passed over 

 some important reasons which exist for maintaining the 

 separate terms originally proposed by His. 



In the first place, the word is not quite so ridiculous, ety- 

 mologically,.as it is represented to be by Dr. Foster. The 

 word endothelium is obviously a contraction of endo-epithe- 

 lium, and means an epithelium which is within (evSov or 

 evTog, intus) or internal, i. e. it means precisely what His 

 intended to signify, and is only so far a misnomer as (epi)- 

 thelium is concerned, since it covers " surfaces of which one 

 great characteristic is that they are devoid of papillae ;" but, 

 as Dr. Foster says, this extension of the meaning of Ruysch's 

 original terms epithelis (of which epithelida is the accusative 

 case) and epithelia " may be easily allowed." Endothelium 

 does not mean " that which is inside a papilla" any more 

 than entoderm means " that Avhich is inside a skin ;" endo- 

 plast, " that which is inside a formation ;" or even entozoon, 

 "that which is inside an animal." The real meaning of 

 these terms Dr. Foster will, doubtless, admit to be "an 

 internal skin, formation (nucleus), and animal." The 

 etymological objections, therefore, do not hold. 



Let us now consider, shortly, whether the physiological 

 diiferences between epithelium and endothehum are sufficient 

 to warrant the use of separate terms. 



Dr. Foster says that endothelium cannot be employed to 

 denote the epithelium derived from the mesoblast, " for it 

 would then include structures still called epithelium, and 

 differing in no essential characters from the epithelium 

 derived directly from the hypoblast.'^ But we should not 

 forget that the mesoblastic origin of geni to-urinary epithe- 

 lium may be more apparent than real. Waldeyer^ has sug- 

 gested that its real origin is most probably from cells of the 

 epiblast, which have become mixed with those of the meso- 

 blast at the time of the formation of the primitive groove. 

 This view is not, of course, susceptible of actual demonstra- 

 tion ; but it is known, at any rate, that the mesoblast becomes 

 closely fused with the epiblast in the region of the axial cord 

 of His, and then again separates ; and that it is after this 

 separation that the Wolffian and Miillerian ducts are formed. 

 It is therefore quite possible that the cells lining these 

 organs and their derivatives may be really derived from the 

 epiblast. Physiologically, at any rate, they are true epithe- 

 lium, and not endothelium, i. e. they are concerned with 

 secretion, which is never the case with endothelium. The 

 small quantity of fluid which bathes the surface of serous 

 > 'Eierstock und Ei,' pp. 113—114. 



