THE SYMPATHETIC SYSTEM 121 



the hemo lymphatic organs, due to infections or auto 

 intoxication of infancy: syphilis and tuberculosis would 

 seem to be the most important. The disease occurs often 

 in association with rickets and enlargement of the spleen. 

 Very often however, it is an isolated affection observed 

 among apparently healthy children without any evidence 

 of rickets or any other disease. 



PATHOLOGICAL ANATOMY. 



The weight of the thymus varies between 25 and 200 

 grams. The gland may keep its normal aspect; that is, 

 simply enlarged. Sometimes it is red, congested, more 

 resistant than normal and filled with fluid when incised. 

 The histological examination then reveals the reactions 

 to an infection of the thymus: lymphocytes replaced by 

 mononuclears, polynuclears, myeclocytes, corpuscles of 

 Hassal showing recent degenerations. The blood vessels 

 are dilated, filled with red cells, the tissues sometimes con- 

 tain hemorrhagic foci visible to the naked eye. 



PATHOGENESIS. 



How does a hypertrophy of the thymus cause respira- 

 tory difficulties? The trachea is the first organ to which 

 attention is drawn. Its compression has shown during 

 life by means of the tracheoscope : Jackson noticed its 

 flattening at the superior level of the thorax. The opera- 

 tive observations in the course of thymedectomy and num- 

 erous autopsies have shown the trachea bent, flattened 

 and crushed. To see these changes at autopsy it is neces- 

 sary to take certain precautions, as due to its elasticity, 

 the trachea will take up its normal position again, as soon 

 as the thorax is opened. It is necessary to remove, as one 

 mass, the thymus, the trachea and the large vessels and 

 fix this mass in formaldehyde before studying the relation- 



