PATHOLOGY OF THE THYMUS 389 



the gland, namely, in the superior pole and in the cortical substance. That 

 this is not always the case, however, has been proved by Pigache and 

 Beclere, as shown later. 



It was Remak, who, in 1855, was the first to notice the existence in the 

 thymus of cysts lined with ciliated epithelium in cats. Watney, in 1883, 

 observed them in dogs, Capobianco (a) (&), in 1892, in the cat, Tourneux 

 and Verdun, in 1897, in human fetuses, Von Elner, in 1902, Hammar 

 (&), in 1905, in the cat, dog, chicken, and frog. Dustin (a), in 1909, 

 observed them in the thymus of lizards. In 1896, Nicholas found ciliated 

 cysts not only in the thymus, but also in the parathyroids. 



Pigache and Beclere, in 1911, observed similar cysts in a dog, two 

 rabbits, and a mouse. These cysts were nearly always found in the medul- 

 lary portions of the thymus. They were extremely irregular in char- 

 acter and the cells which constituted their lining were in turn cylindrical, 

 cuboid al, or pavimentous. These three forms of epithelium were usually 

 combined in the same cyst. Many of these cells were ciliated, but by no 

 means all of them, and the ciliated ones were disposed in a very irregular 

 way. The lumen of the cyst contained a mass of cellular detritus showing 

 all stages of degeneration. 



In adults, cysts of the thymus are very rare. Hueter, however, re- 

 ported a very interesting and unique case of a large cystic formatior 

 in an adult. The tumor was 76 mm. long and 28 mm. wide. It was 

 polycystic, resembling in every respect a bunch of grapes. The tissue 

 between the cysts was absolutely normal and contained a great many Has- 

 sall's corpuscles. The connective tissue was more or less marked and scle- 

 rotic. In the cyst itself polypoid arborescences and cholesterin were pres- 

 ent. Nothing suggestive of malignancy in these cysts was present. Sim- 

 ilar observations have been made in animals. 



Hueter observed small thymic cysts in individuals between eighty 

 and ninety years of age. No syphilis was present. These small cysts 

 were the size of a pea, contained a great deal of cholesterin and were lo- 

 cated in a fatty mass supposed to be the thymus. That it was really so, 

 was revealed by the fact that the microscope showed the typical structure 

 of the thymus. 



Chiari (&) (&) thinks that congenital cysts are due to cystic degenera- 

 tion of HassalPs corpuscles. Eberle thinks they take their origin in unob- 

 literated segments of the excretory canals of the thymus. Tuve believes 

 that the cysts are of syphilitic origin and are formed by necrosis of paren- 

 chyma becoming surrounded by an inflammatory zone which is finally 

 converted into a thick capsule lined with a low cuboidal epithelium. 



Congenital Syphilitic Cysts. These cysts are lined with a squamous 

 cell epithelium and contain a. great deal of more or less degenerated cellu- 

 lar tissue and frequently some pus. They are often known as "Dubois 

 abscesses." (See Syphilis of the Thymus.) 



