GLANDS. 



67 



Remak was first established the law that the formation 

 of glands in general must be regarded as consequent 

 upon a direct process of proliferation on the part of 

 epithelial structures. Previously large quantities of ' 

 cytoblastema had been conceived to exist, in which, 

 spontaneously, glandular substance took its rise ; but, with 

 the exception of the lymphatic glands, and perhaps those 

 belonging to the sexual organs, their mode of origin is 

 everywhere this that at a certain point, in a manner 

 very similar to that which I described to you in the fore- 

 going lecture, when speaking of the excrescences of 

 plants, an epithelial cell begins to divide, and goes on 

 dividing again and again, until by degrees a little process 

 composed of cells grows inwards, and, spreading out 

 laterally, gives rise to the development of a gland, which 

 thus straightway consitutes a body continuous with lay- 

 ers of cells originally external. Thus arise the glands of 

 the surface of the body (the sudoriferous and sebaceous 

 glands of the skin and the mammary gland), and thus 

 also arise the internal glands of the digestive tract (the 

 stomach glands and liver.) The most simple forms which 

 glands can present do not occur at all in man. In infe- 

 rior animals, however, uni-cellular glands have recently 

 been discovered. The glands of the human body are 

 invariably made up of a number of elements, which can, 

 however, ultimately be traced back to a nearly simple 

 type. Besides, in our own glands, in consequence of 

 their size and complicated structure, other necessary 

 constituents generally enter into their composition, so 

 that, regarded as organs, they certainly do not consist of 

 gland-cells only. But all parties are now pretty well 

 agreed that the gland-cells are the really essential ele- 

 ments, just as the primitive bundles are in muscle, and 

 that the specific action of a gland is dependent upon the 

 properties and peculiar arrangement of these elements. 



