CHAPTER VII 

 THE THYMUS GLAND 



THE STRUCTURE AND DEVELOPMENT OF THE THYMUS 



RELATIVELY to the rest of the body the thymus is largest at birth, but it 

 remains well developed during childhood. It is essentially an organ of 

 early life. After puberty it generally undergoes retrograde changes ; these 

 consist in diminution in volume of the proper gland substance accompanied 



FIG. 28. Part of lobule of the thymus of a child. Magnified 60 diameters. 

 c., cortex ; m., medulla ; 6., b., large blood-vessels in connective tissue trabeculee. 



by an increase in connective tissue, the whole organ becoming smaller and 

 often embedded in a mass of fat. Occasionally it remains fully developed ; 

 such cases are generally associated with an unusual development of lym- 

 phatic tissue in the body, the condition being termed status lymphaticus. 



In its developed condition the thymus consists of two main lobes, one 

 on each side, the lobes themselves being subdivided into lobules and the 

 whole strung together in an irregular manner along a strand of connective 

 tissue which sends offsets into the lobes, subdividing the lobules from one 

 another and sending partial septa into the individual lobules. The con- 



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