Eyelids and Lachry mal Apparatus of Birds. 
17 
The course of the tears, i. e. } the secretion mainly of Harder's 
gland, is quite different from the lachrymal drainage in Man. 
Although several writers speak of the avian lachrymal fluid as 
passing into the nose through the lachrymal canals, or of passing 
into the posterior nares, these statements are misleading, if not 
untrue. The accompanying figure, representing dissections of a 
number of avian species, demonstrates that unless one includes the 
median cleft at the roof of the mouth as an integral part of the 
nares, the lachrymal duct of Birds has little to do with the nasal 
passages, but is an isolated tube carried through and past the nasal 
structures, terminating in and emptying directly into the oral 
cavity (mouth). The buccal or oral cavity, as is well known, is a 
receptacle that includes and is not separated from the c-hoana, the 
pharynx and the larynx. 
Fig. 11 — Enlarged View of a Cross Section of the Head at the Base of 
the Beak about 2 mm. Anterior to the Eyes to Show the Lachrymal Ducts. 
The lower Mandible has been Removed. (Wood and Slonaker.) 
AA, Right and left air passages connecting external nares and the 
buccal cavity, BC, through the choana, P; F, frontal sinus; J, organ of 
Jacobson; L, lachrymal ducts which open by horizontal slit-like openings 
into the choana; the anterior wall of the right duct has been cut away; 
M, maxillary sinus; T, turbinals. 
Hoffman (Die Tranenwege der Vogel und Reptilien, Inaug. 
Diss., Halle, 1882) observed on the lids peculiar grooves leading to 
the punctal openings, evidently intended as accessory drainage 
gutters, to assist in directing and carrying the lachrymal secretions 
into the eanaliculi. 
The orifices of the eanaliculi, upper and lower, are, as stated, 
not placed on the lid margins at the anterior canthus, but generally 
open a few millimetres from it by gaping mouths that are unpro- 
vided with connective tissue plates or muscle fibres, as found in Man. 
Minute shallow grooves, better shown in the Hen. lead from the 
canthus around and close to the margins of both lids and form a 
