400 THE SOLIDS. 



which they have been formed probably by the development of 

 fresh cells behind them, so that in general the sebaceous 

 secretion consists of an aggregation of such eliminated cells. 

 Some few of the cells, however, do burst and allow of the 

 escape of their contents. 



The sebaceous cells, like other secreting cells in an early 

 stage of development, are granular and nucleated. 



In the character of their secretion, the sebaceous glands 

 exhibit considerable affinity with the mammary glands. The 

 milk globules, however, are formed without the cells, and 

 not within them, as is the case in the sebaceous glands. 



The sebaceous glands, exclusive of the ceruminous, manifest 

 considerable variety in size, form, and arrangement. They 

 may be thus arranged : first, The Meibomian glands ; second, 

 The glands of the Hair Follicles, the hairs being in some cases 

 present in the follicles, and in others absent from them ; 

 third, The glands of the Nipple ; fourth, The glands of the 

 Prepuce ; and fifth, The glands of the Caruncula3 Lachry- 

 males. 



Meibomian Glands. 



The Meibomian glands are situated on the inner surface 

 of the eyelids, between the conjunctiva and the tarsal car- 

 tilages ; they are of an elongated form, and disposed in a 

 vertical manner. 



The number of these glands in the two eyelids is usually 

 not less than forty ; in one instance I counted eighteen in the 

 upper eyelid, and twenty-two in the lower. Their general 

 form and arrangement differs somewhat in the two eyelids ; 

 thus, in the lower, they are of nearly equal length, and are 

 arranged in a parallel manner, while in the upper they are 

 much longer, almost as long again, their origins describing 

 an arc ; and in place of being disposed parallelly, they radiate 

 from each other. These differences depend upon the cor- 

 responding differences in the size and form of the two eyelids. 



Each gland consists of a number of follicles or sacks which 

 open into a central canal, which pierces the conjunctiva! 



