2/6 SECRETION 



2. Follicular Glands. Examples of these are the simple mucous 

 follicles and the simple follicles of Lieberkiihn. 



3. Tubular Glands. Examples of these are the ceruminous glands, 

 the sudoriparous glands and the kidneys. 



4. Racemose Glands, Simple and Compound. Examples of the simple 

 racemose glands are the sebaceous and Meibomian glands, the tracheal 

 glands and the glands of Brunner. Examples of the compound race- 

 mose glands are the salivary glands, the pancreas, the lachrymal glands 

 and the mammary glands. 



5. Ductless, or Blood-Glands. Examples of these are the thymus, 

 the thyroid, the suprarenal capsules and the spleen. 



The liver is a glandular organ that can not be placed in any one of 

 the above divisions. The lymphatic glands and other parts connected 

 with the lymphatic and the lacteal system are not true glandular organs. 

 These are sometimes called conglobate glands. 



The general structure of secreting membranes and of the follicular 

 glands is quite simple. The secreting parts consist of a membrane, 

 usually homogeneous, covered on the secreting surface with epithelial 

 cells. Beneath this membrane ramify the bloodvessels which furnish 

 materials for the secretions. The follicular glands are simply digital 

 inversions of this structure, with rounded blind extremities, the epithe- 

 lium lining the follicles. 



The tubular glands have essentially the same structure as the fol- 

 licles, except that the tubes are long and more or less convoluted. The 

 more complex of these organs contain connective tissue, bloodvessels, 

 nerves and lymphatics. 



The compound racemose glands are composed of branching ducts, 

 around the extremities of which are arranged collections of rounded fol- 

 licles, like bunches of grapes. In addition to the epithelium, basement 

 membrane and bloodvessels, these organs contain connective tissue, 

 lymphatics, non-striated muscular fibres and nerves. In the simple 

 racemose glands the excretory duct does not branch. 



The ductless glands contain bloodvessels, lymphatics, nerves, some- 

 times non-striated muscular fibres, and a peculiar structure called pulp, 

 which is composed of liquid with cells and occasionally with closed 

 vesicles. These are sometimes called blood-glands, because they are 

 supposed to modify the blood as it passes through their substance. 



The testicles and the ovaries are not simple glandular organs; for 

 in addition to the production of mucous or watery secretions, their prin- 

 cipal office is to develop certain anatomical elements, the spermatozoids 

 and the ova. The physiology of these organs will be considered in 

 connection with embryology. 



