EFFECTS ON THE THYMUS 29 1 



deux modifications importantes: /' inversion thymique et la sclerose marquee, 

 les deux alterations se rencontrent dans le meme organe a, differents degres, 

 suivant les cas." He described epithelioid cells and giant mononuclear cells 

 as abundant in the cortex during thymic inversion, with peripheral invasion 

 of the lobule by adipose tissue. 



Nobecourt ('16) reviewed the changes in the thymic atrophy of malnourished 

 infants, following in general the findings of Lucien, Feldzer and Mattei. He 

 noted that the nature of the thymus atrophy has been explained in three ways: 

 (1) as a primary cause. of the general malnutrition (Farret, Durante, v. 

 Mettenheimer) ; (2) as a simple, secondary atrophy, comparable to that occur- 

 ring in other organs during inanition (Friedleben, Clark, Ghika, Seydel, Sokoloff) ; 

 and (3) as due to toxic or infectious causes (Tixier, Feldzer, Martel, Marfan). 



Hart ('17) described the thymus in a starved child of 3 years, complicated 

 with " eine floride Rachitis leichten Grades." The thymus weighed 5 g. Frozen 

 sections stained with Sudan showed no sclerosis, but numerous peripheral 

 cells with vesicular nuclei filled with fatty droplets of variable size, and some 

 cells with complete fatty degeneration. In the center of the lobules, Hassall's 

 corpuscles contained fatty detritus, but cells with fatty degeneration were rare. 

 The cells in the septa were mostly fat-free. The ordinary stains (hematoxylin, 

 etc.) showed the typical inversion of the lobule, with lighter cortex and darker 

 medulla. 



Hammar ('21) has recently reviewed the problem of thymus involution, 

 including the accidental involution caused by disease, pregnancy, X-rays, and 

 especially inanition. In congenital pyloric stenosis and in infantile pyloro- 

 spasm, accurate measurements showed the thymic parenchyma reduced 80 per 

 cent. In general, the cortex is more labile, being rapidly reduced by wholesale 

 emigration of lymphocytes, which infiltrate the adjacent interstitium and 

 vessels. The medulla also becomes richer in lymphocytes. The number of 

 mitoses is greatly reduced; but a few persist, especially in the reticulum cells. 

 The distinction between cortex and medulla apparently disappears, although 

 fat stains show abundant fat droplets appearing in the cortical reticulum. The 

 medulla may become relatively richer in nuclei, producing the "inversion" 

 of the French authors, which appears oftener in illness than in starvation. 



During inanition-involution, according to Hammar, the medulla remains 

 unchanged longer than the cortex, but later decreases in size by general atrophy 

 (and some degeneration) of the individual medullary cells. Hassall's corpuscles 

 are more resistant, hence become relatively more numerous, although there is a 

 slow decrease in absolute numbers. In extreme cases the parenchyma may 

 decrease to 1 or 2 per cent of the original amount, and the thymus presents only 

 narrow strips, poor in lymphocytes, and in which Hassall's corpuscles may disap- 

 pear entirely. During Rontgen involution, the lymphocytes do not emigrate, 

 but disintegrate in situ. There are also some variations in the process of involu- 

 tion in different diseases, but in general the process resembles that of inanition- 

 involution. (Hammar '17, '18, '20, '21.) 



In famine-stricken children of various ages, Nicolaeff ('23) found the thymus 

 90-98 per cent subnormal in weight, compared with Hammar's norm for age. 



