GLANDS 



219 



The Meibomian glands, belonging to the group of sebaceous 

 glands, are confined to the Mammalia, and lie embedded in the 



Fie. 175a. — Diagram to illustrate the shiftinc; of the Lachrymal Gland 



WHICH has taken PLACE IN THE COURSE OF PhYLOGENY. 



The gland shifts in the direction of the arrows ; a, its position in the Amphibia ; 

 6, in Reptiles and Birds, and occasionally in Man, in which case it may be 

 regarded as atavistic ; c, normal position in Man. 



substance of the eyelids in the form of branched tree-like tubes 

 or clustered masses. They open on the free edge of the lid, and 

 produce a fatty secretion. Certain modified sweat-glands known as 



Fig. 175b. — Diagram of the Lachrymal Apparatus of AIan. 



TD, lachrymal gland, divided up into several portions ; **, ducts of the lachrymal 

 gland ; tt, puncta lachrymalia ; TR, TR^, upper and lower lachrymal canals ; 

 8, lachrymal sac ; D, naso-lachrymal duct. 



the glands of Moll are also present immediately within the eyelids 

 of Mammals. 



The naso-lachrymal duct, which conducts the lachrymal 

 secretion into the nose, has already been referred to (p. 201). 



