MORBID ANATOMY. - Not much is known, and probably there is not much to be known, respecting the morbid conditions of the thymus. Absence of the gland has only been observed in cases of acephalism, where the brain and many other parts are simultane ously deficient, while in cases of anence phalism, where the brain is also wanting wholly, but the general development much more complete, the thymus is present ; no thing therefore can be concluded from its absence in cases of extreme monstrosity as Mr. Simon has well observed.
Inflammation of the gland, if it ever happens, is of rare occurrence. Professor Hope,however, refers to a case by Mason, in which an abscess of the thymus is said to have opened into the trachea.
The same author states that Becher and Hangstadt have collected about fifteen ex amples of persons, of different ages, affected with more or less general tubercular disease, in whom the thymus was found involved. " It was for the most part considerably en larged, very firmly united with surrounding parts, and either converted by tubercular in filtration into a hardened mass, or else par tially destroyed by tuberculous softening. In three or four instances calcareous concretions, probably resulting from the retrogression of tubercle, were discovered in the gland." Haller speaks of the thymus as being fre quently affected with scirrhus along with the conglobate glands ; but though Becher gives an instance on his own authority, and refers to others, there can be no doubt that true malignant disease of the gland is extremely rare. Sir A. Cooper gives a case, in which death was produced by the pressure of an enlarged thymus upon the vena transversa and upon the trachea, probably also upon the vagi nerves ; there was severe dyspncea and mdema of the lower extremities. He considers
the disease to have been of the fungoid kind, i. e. encephaloid.
Atrophy of the thymus occurs as a normal event ; if, however, it should take place long before the usual period, determined, as we have seen, not so much by the lapse of time as by the condition of the system, it must be regarded as morbid. Yet in every such case it is almost certain that the atrophy of the thy mus would be but part of a general malady, wherein the nutrition of every organ was greatly impaired.
Hypertrophy of the thymus has attracted more attention, Dr. Kopp having noticed several cases of suddenly fatal dyspncea oc curring in children, in whom the gland was found of large size, concluded that there was some essential connection between the glan dular enlargement and the suffocative pa roxysms. The fallacy of this opinion has been well pointed out by Mr. Simon and others. I must refer to his work, and that of Professor Hope, for a full account of their arguments, and will only mention two circumstances, which seem to me conclusive upon the point. The first is, that "thymic asthma" may occur with an unnaturally small thymus ; the second, that when a thymus, enlarged by malignant disease, as in Sir A. Cooper's case, does oc casion dyspncea, it is not sudden and pa-"` roxysmal, but constant and exhausting.