EFFECTS ON THE THYMUS 289 



sometimes nearly all disappear. " Die Retikulumzellen legen sich dabei dichter 

 an und bilden haufig sogar Komplexe, die ihr urspriingliches epitheliales Aus- 

 sehen mehr oder weniger wiedergewonnen haben. Auch sie fallen einer Degen- 

 eration allmahlich anheim, welche allerdings von dem normalen durch Hyper- 

 trophic der Zellen eingeleiteten und zur Bildung Hassal'scher Korperchen 

 fiihrenden Prozess deutlich zu trennen ist." Hassall's corpuscles persist in the 

 earlier stages of inanition, becoming relatively prominent; later they are vari- 

 able, sometimes disappearing. 



Bovaird and Nicoll ('06) studied the weight and gross structure of the 

 thymus in 571 autopsies on children up to 5 years of age. In general, the loss 

 in thymus weight (80 or 90 per cent, in extreme cases) is relatively greater 

 than in body weight; but there are exceptional cases indicating that factors 

 other than the extent of malnutrition may influence the weight of the organ. 

 The greatest loss of thymus weight occurs in marasmus, diarrheas, and similar 

 chronic exhausting disorders. The atrophic involution includes actual absorp- 

 tion of thymic tissue, which becomes fibrous and fatty, as during the normal age 

 involution. 



Thompson ('07) in 20 cases of infantile marasmus found the average weight 

 of the thymus 2.472 g. (range 1.0-4.75). There is marked histological 

 atrophy of the lymphoid tissue, and increase of interlobular connective tissue, as 

 described by Dudgeon. Hassall's corpuscles become prominent and the differ- 

 entiation between cortex and medulla usually disappears. 



Naegeli ('08) held that the disappearance of the medullary cells of the 

 thymus during inanition indicates that these are large lymphocytes, rather than 

 epithelial in character. 



Lucien ('08, '08c), in fatal cases of athrepsia, found an average thymus 

 weight of only 0.97 g. (range 0.05-2.50), indicating an average loss of over 80 

 per cent. Grossly the thymus appears reddish, with a firm, fibrous consistence. 

 The histological changes are variable, with 4 progressive stages: (1) Early 

 involution, with retention of the distinction between cortex and medulla; little 

 change in structure, aside from increased perilobular connective tissue and dila- 

 tion of blood vessels. (2) The cortico-medullary distinction disappears; 

 lymphocytes equally distributed throughout, but the medulla is more vascular 

 and contains more Hassall's corpuscles. (3) The peripheral (cortical) zone 

 becomes clear, filled with irregular "epithelioid" cells, and the lymphocytes 

 become more concentrated in the central (medullary) zone, making an inver- 

 sion of the lobular structure; Hassall's corpuscles numerous throughout almost 

 the entire lobule, appearing simple or compound in structure, and in various 

 stages of evolution or degeneration, sometimes hyalin, cystic or calcified. (4) 

 The most extreme stages show the thymus converted into a fibrous tract, with 

 numerous thick- walled vessels ; vestiges of the thymic lobules appear as scattered 

 small lymphoid nodules; sometimes a few degenerating Hassall's corpuscles are 

 still visible. 



Feldzer ('10) and Tixier and Feldzer ('10) concluded that the thymic 

 atrophy in athrepsia is probably secondary, rather than primary in character. 

 The regressive process is a sclerosis, distinct from the normal adipose age 



