INTRODUCTORY. 19 



Simple follicular glands are flask-shaped bodies openini,^ 

 on to the surface bj a small duct ; when several of these 

 pour their secretion into a compound duct, we see the first 

 example of a compound follicular or racemose gland, 

 which consists of a number of flask-shaped or vesicular 

 bodies, which pour their secretions through a number of 

 ducts, which unite and reunite until at last thej form a 

 more or less elongated canal, the duct of the gland, which 

 opens on to the surface of the mucous membrane lining 

 the cavity to which the gland is appended. The secreting 

 vesicles or acini thus bear to the ducts the relation which 

 grapes bear to their stalks, hence the name racemose. 

 The several parts of the gland are closely invested by 

 areolar tissue, whereby they are united to form lobules, 

 which by their union complete the gland. As examples of 

 compound follicular glands, may be adduced the salivary, 

 pancreas, lachrymal, and mammary glands, while the 

 meibomian, brunners, and the sebaceous glands present 

 this type under a much less complex form. 



The so-called ductless glands present peculiar charac- 

 ters, which will be specially noticed. All the above- 

 mentioned structures are supplied with matter for growth 

 and for rej)air by the blood, and the same fluid also re- 

 moves matters for which they have no longer use. It is 

 conveyed from the heart throughout the system by cer- 

 tain vessels found in all parts of the body more or less. 

 It must, however, be clearly understood that in all cases 

 the special cells of a tissue are externally placed to the 

 blood-vessels, so that all nutriment obtained by any but 

 blood-cells must be obtained through the walls of the 

 vessels and through the wall of the cell. The vascularity 

 of a part consists in the close relation of its cells to its 

 vessels. Thus the capillaries run between the muscular 

 fibrillae of voluntary muscle ; they are separated from the 

 cells by basement membrane in the complex membranes ; 

 in stratified epithelium the outer layers are separated by 

 basement membrane and a number of cells which hand on 

 the nutritive portion or plasma of the blood from within 

 outwards. The same condition obtains in cartilage except 

 that the cells are separated by intercellular substance of 

 variable nature and amount ; while in bone the plasma 

 passes through an elongated but extremely minute canal 

 m its course from the vessel to the cell. The vessels from 



