PATHOLOGY OF THE THYMUS 385 



they were more or less transformed into small cystic nodules. At the 

 same time, Hassall's corpuscles were increased in number and size, so 

 much so that some of them were confluent and fused together to form a 

 cavity. The connective tissue underwent a sclerotic process. The paren- 

 chyma was separated by void spaces of various sizes. 



In 1905, Fortescue and Brickdale examined 20 cases of children who 

 died from acute diseases such as pneumonia, diphtheria, peritonitis, etc., 

 and found that in some cases involution of the thymus was present while 

 in some others hyperplasia had occurred. 



In 1909, Ronconi, examining two cases of diphtheria, found an in- 

 creased volume of the thymus and increase in the number of Hassall's 

 corpuscles. Some of these corpuscles showed retrogressive changes. 



In 1910, Marfan (c), examining the thymus of patients who 'died from 

 diphtheria, erysipelas, variola, infectious purpura, etc., found thymic 

 hyperplasia with increased number and size of Hassall's corpuscles and 

 eosinophiles. The same findings were reported by Pappenheimer (a), in 

 1910. Holdstrom reported the same findings in 1911. 



K. Takeuchi (a) studied experimentally the reaction of the thymus to 

 acute infections in 57 rats, which were injected with colon bacilli. He did 

 not observe, as is usually the case in human beings, any inflammatory 

 hyperemia and hemorrhages of the thymus. He noticed that the cortical 

 and medullary substances lost their well established differentiation. The 

 thymic cells, at first, became hyperplastic, then showed degenerative 

 changes and resorption, so much so that in the last stage there remained 

 practically only connective tissue and Hassall's corpuscles. He did 

 not observe any increase in the number and size of HassalFs corpuscles and 

 of the eosinophiles, as happened in thymic infections in human beings. 



In 1912, Hart basing his conclusions upon 100 cases, reported the 

 same findings, namely, in a great number of cases an increased hyperplasia 

 of the thymus, increase in size and number of the Hassall's corpuscles, and 

 increase of the eosinophiles. In diseases of long standing and of severe 

 type, the damage done to the thymus is irreparable; pathological involu- 

 tion takes place, connective tissue infiltration invades the thymus after 

 which a fatty degeneration takes the place of the thymus. 



In 1914, Oliari examining the thymus of 25 individuals who had 

 died from various diseases such as tuberculosis, pleurisy, pneumonia, etc., 

 observed hyperplasia of the thymus, sclerosis of the gland, and in a gen- 

 eral way, marked regressive changes. 



In 1918, Hammar reported the results of his researches of 21 cases 

 that died from diphtheria and came to the conclusion that in diphtheria 

 the thymus undergoes an accidental involution in which more or less 

 marked regressive changes are observed, but in which the number and 

 size of Hassall's corpuscles are increased. 



