50 HISTOLOGY. 



two products being entirely different (e. g., the liver, the 

 pancreas, and the testes). For a fuller discussion of internal 

 secretion and its great influence in the general economy, the 

 reader is referred to works on physiology, to which this subject 

 truly belongs. 



Glands may also be classified according to their products 

 into those secreting cells (ovary, and sebaceous glands), and 

 those secreting fluids. The glands of the first class either 

 cast out whole cells, or the cells break and their contents are 

 secreted, the cell going to pieces and forming a part of the 

 secretion. To this class belong the sebaceous glands, mam- 

 mary glands, testes, ovaries, and large sweat glands. Those 

 of the second class secrete a material from cells which do not 

 disintegrate, but retain the power of producing this secretion 

 many times. A sharp line of distinction cannot be drawn 

 between these two classes, for cells secreting fluids may also 

 under other circumstances be wholly or partially cast off them- 

 selves. 



We shall now consider certain elements which go to make 

 up glands in general. At the outer side the cells of the 

 glandular epithelium usually are bounded by a fine membrane 

 (membrana propria or m. basilaris). This usually shows no 

 details of structure, and it is doubtful whether it is a product 

 of the cells or whether it is of connective-tissue origin. In 

 some cases it contains flat stellate cells which surround the 

 gland body like a basket, and join together by processes. These 

 are called basket cells. 



Many authors consider the membrana propria to be made 

 up of connective-tissue elements ; others have found in it con- 

 tractile muscle elements which have the power of drawing 

 together and pressing the secretion out of the gland. 



Compound glands are divided usually by means of strands 

 of connective tissue into lobules; from each of which a duct 

 emerges to pass into the main duct. Outside the membra na 

 propria blood- and lymph-vessels and nerves are present in the 

 connective tissue. Also we find in some glands tvpical smooth 

 muscle fibres under the membrana propria. Often around the 



