THE LACHRYMAL GLAND 149 



work on my part, and I decided that a detailed study of the 

 structure of this gland in one species might well precede a general 

 comparative study. 



In view of the work already begun on the Harderian gland in 

 Bos and the availability of the lachrymal gland in this species 

 for both structural and chemical study, it was chosen for this 

 purpose. 



Numerous contributions have appeared dealing with various 

 phases of the lachrymal gland of different animals — such as its 

 phylogeny, embryology, innervation, gross and microscopic 

 structures, etc. Chief efforts, , however, have been directed 

 toward the study of the structure of the cells and the secretory 

 changes they undergo during the stages of rest and activity. 



The origin and distribution of the gland in vertebrates have 

 be«n described by Wiedersheim (76) and Sardemann ('87). 

 Wiedersheim ('07) states: 



The first attempt of a vertebrate to exchange an aquatic for an 

 aerial existence necessitated the development of a secretory apparatus 

 in connection with the eye. Thus in Urodeles a glandular organ is 

 developed from the conjunctival epithelium along the whole length of 

 the lower eyelid ; in Anurans and Reptiles this becomes more developed 

 in the region of the anterior, and in many Reptiles also of the posterior 

 angle of the eye, the original connecting bridge gradually disappearing: 

 thus two glands are developed from the primitively single one, each of 

 which becomes further differentiated both histologically and physio- 

 logically. From one is formed the Harderian gland — anterior angle 

 of the eye — while the other, posterior angle, gives rise to the Lachrymal 

 gland. In Crocodiles, Snakes, and Hatteria, the lachrymal gland is 

 wanting while in the Chelone it is extremely large. 



Further contributions regarding the comparative anatomy of 

 the lachrymal gland are given by Van Trotzenburg ('01) who 

 studied it in both the old and new world monkeys and its phy- 

 logenetic relation to man. 



Contributions to the embryology of this gland and its accesory 

 structures have appeared from time to time. Falchi ('05) 

 studied the development of the gland in the rabbit, guinea pig, 

 sheep, and human. Monesi ('03) , Matys ('05) , ('06) , Kiisel ('06) , 

 and Lang ('11), also, have contributed to this phase of the sub- 

 ject. Their efforts, however, have been concerned chiefly with 



