4 J. PARSONS SCHAEFFER 



Ewetzky ('79) studied the embryology of the nasolacrimal 

 connections in ' Rindsembryonen' and in the main agreed with 

 Born's findings. 



Born ('82) investigated reptiles and found that the solid cord 

 or strand of epithelial cells retained connection with the surface 

 epithelium at the ocular end, but that the nasal end of the naso- 

 lacrimal duct grew as a sprout from the mother cord of cells. 

 He also found that there is no doubling or pairing at the ocular 

 end; that is, he found but one lacrimal duct. 



Legal ('83) investigated the pig and came to the same general 

 conclusion as did Born, and claimed (for pig) that the superior 

 lacrimal duct was wholly a part of the original mother cord of 

 cells. He further claimed that the mother cord of cells retained 

 superiorly and dorsally a connection with the epidermis in the 

 region of the palpebral fissure. 3 He concluded that the inferior 

 lacrimal duct grew as a sprout from the mother cord, but he 

 found that the sprout did not reach the free border of the inferior 

 eyelid; therefore remaining 'funktionell unbrauchbar.' 4 



Kolliker ('84) believed that both lacrimal ducts developed as 

 sprouts from the mother cord. 



Ewetzky ('88) thought that the ocular end of the mother cord 

 divided into two forks, and that these forks in turn developed into 

 the lacrimal ducts (superior and inferior). 



Jouves ('97) studied the sheep and man, and found in a 19 mm. 

 human embryo both lacrimal ducts present but without any con- 

 nection with the surface epithelium at this time. 



Cosmettatos ('98) investigated the rabbit, and Stanculeanu 

 ('00) the bird, the sheep, and man. These investigators, accord- 



3 . . . . ganz hinten endlich bleibt bestandig eine Verbindung mit der 

 Lidfurche erhalten. 



4 Bei Schweinsembryonen ist die Thranenkanalanlage eine solide, von der 

 tiefenEpidermisschicht des Thranenfurchengrundes ins Bindegewebe einwuch- 

 ernde Leiste, die sich bis auf das hinterste Ende am innern Augenwinkel von der 

 Epidermis abschniirt, und mit dem vordern, stark auswachsenden Ende mit der 

 Nasenhohle verbindet: der abgeloste, solide Epithelstrang stellt den spatern 

 einfachen Thriinennasengang und das obere Thranenrorchen dar, das untere 

 sprosst aus demselben hervor, bleibt aber, da es die freie Lidflache nicht erreicht, 

 funktionell unbrauchbar. 



