LESSON 96.] THE EYES IN MAMMALIA AND MAN. 



313 



each gland is seen to consist of a basement mem- Fl - 445 - 



brane (a), and an epithelium (6) containing seba- 

 ceous matter ; c represents the orifice of the duct. 

 These glands are subject to disease, especially in 

 children, which appears to partake of a congested 

 character; the secretion is suspended, and the 

 ducts closed up ; in this form of disease the mar- 

 gins of the lids become inflamed, and the loss of 

 the eye-lashes invariably follows. 



1418. Thus we have seen these complicated 

 optical instruments, the most universal in their 

 distribution in the animal kingdom, and by far the 

 noblest organs of sense, gradually advancing to 

 perfection, from the animals of lowly organization, 

 in which we first found them, up to man, where all 

 their internal essential parts, and their external 

 accessory apparatus, are the most exquisitely fin- 

 ished, and most minutely adjusted. It is chiefly 

 through their means that he is connected to the 

 external world, that he is enabled to provide for 



A MeiDomian gland, re- 



his wants, to acquire the materials of thought, moved and magnified. 

 to enjoy the sublime spectacle of the starry Heavens, and to gaze 

 with fervent admiration upon the wonders and beauties of ever 

 changing Nature, as revealed to him in this magnificent World ! 



