INANITION AND MALNUTRITION 



series of 18 malnourished infants. They also studied the histological changes in 

 the thymus, finding a general fibrosis, with thickening of the capsule and inter- 

 lobular connective tissue. Hassall's corpuscles increase in size and undergo 

 hyalin degeneration. A later stage shows "almost entire disappearance of the 

 lymphoid structure of the lobule and an increase in the reticular endothelium." 

 Dudgeon ('05) studied the weight and structure of the thymus in 15 cases of 

 primary infantile atrophy and in 41 cases of secondary atrophy. He concluded 

 that the atrophy of the thymus is closely associated with the general wasting of 

 tissues. Histologically, the most characteristic changes in the atrophic thymus 

 include: fibrosis, usually well marked, with thickening of the outer coat of the 

 blood vessels; atrophy of the lymphoid corpuscles, which are replaced by endo- 

 thelial cells, connective tissue cells and small "giant cells;" all varieties of degen- 

 eration in Hassall's corpuscles. The average weights found by Dudgeon are as 

 shown in the accompanying table. 



Weight of the Thymus in Infants with Various Conditions of Nutrition (Dudgeon'os) 



Source 



Primary atrophy 



Secondary atrophy (tuberculous) .... 

 Secondary atrophy (non-tuberculous) 



Acute diseases 



Fetal specimens 



"Sudden death." "Found dead". . . 



Somewhat similar thymus weights were recorded by Fortescue-Brickdale 

 ('05), who found the average in 12 marantic infants to be 2.45 (1.3-4.8) g.; in 9 

 tuberculous children, 1.9 to 10 g. ; in 9 chronic emaciated (non-tuberculous), 

 3.14 (1-4.7) g-5 m 2 ° acute diseases, 5.7 g. 



Hammar ('05, '06) made an extensive and thorough study of the involution 

 of the thymus, a continuation of his earlier animal experiments (to be mentioned 

 later). Hammar introduced the term "accidental involution" to indicate the 

 atrophy caused by malnutrition or other abnormal factors, in contrast with the 

 normal "age involution" of the thymus. The establishment of a reliable norm 

 of growth in weight made it possible to measure precisely the degree of atrophy at 

 any stage of postnatal development. The amounts of parenchyma and stroma 

 in both cortex and medulla were also measured, making possible a quantitative 

 measurement of the histological changes. 



In general, Hammar found that the process of atrophy in the "accidental" 

 involution is characterized by a subnormal amount of parenchyma, which, in 

 the cortex, may disappear entirely. The stroma is also reduced, but to a lesser 

 degree; it therefore becomes relatively more abundant, but there is no true 

 fibrosis or sclerosis. There may be a "paradoxical" adipose deposit in the 

 stroma of the athreptic thymus, even in infants where normally no fat occurs. 

 In the parenchyma, the lymphocytes becomes variably decreased in number; 



