224 THE DISEASES OF THE THYMUS GLAND 



of Hassal's corpuscles. In addition to this involution of age an accidental 

 involution also occurs; Hammar and Jonson have shown that in fasting ani- 

 mals the weight of the thymus gland reduces very rapidly, especially through 

 loss of lymphocytes. Also in the melting down of the thymus gland on 

 irradiation with X-rays, the reticulum shows itself much more resistant than 

 the lymphocytes. The accidental involution is found among chronic dis- 

 eases that lead to marasmus. It is especially well expressed in pedatrophy 

 (Farret). Also, according to Hammar, accidental involution may occur in 

 older people, an evidence that glandular tissue capable of functionating has 

 still been present. 



Physiology. The question as to whether the thymus gland is an organ 

 important for the life of the organism has not until recent times received 

 a uniform answer. Friedleben, Langerhans, and others saw animals in which 

 the thymus gland had been removed go undisturbed in their development, 

 while other authors on the contrary, of whom I here mention only Tarulli 

 and LoMonaco, Ghika, Cozzolino, Basch, Sommer and Florken; Ranzi and 

 Tandler saw occur in dogs, rabbits, cats, and other animals, temporary 

 serious disturbances of growth which later disappeared. The most recent 

 investigations are those of Klose and Vogt and of Matti. The investigations 

 make it very likely that the disturbances mentioned can no longer disap- 

 pear when the extirpation of the thymus gland has been done on very 

 young animals only a few days old. 



Klose and Vogt operated on twenty-five dogs. The phenomena observed 

 are briefly as follows: After the latent stage of about fourteen days the ani- 

 mals gradually showed a spongy, soft skin, a "pasty habitus." They began 

 to remain behind in growth on account of a lessened growth in length of the 

 extremities. The bones were distinctly more flexible. In agreement with 

 Basch, Klose and Vogt found that the ossification is retarded and that if 

 the bones are fractured callus formation is very poor or does not occur at 

 all. The ash contents of the bones is essentially diminished. Basch also 

 found that in this stage the elimination of calcium is essentially increased. 



The hyperexcitability to galvanism which Basch found in thymectomized 

 animals is to be referred to the associated extirpation of the parathyroid 

 bodies imbedded in the thymus tissue. 



According to Ranzi and Tandler, the dentition is also delayed in this stage ; 

 the dogs take on abundant fat (stadium adipositatis, according to Klose and 

 Vogt). This is followed by a stadium cachecticum; in spite of increased 

 hunger the animals gradually lose weight, muscular tremors occur, the hemo- 

 globin contents and erythrocyte contents of the blood reduce, and chemotactic 

 irritants, such for examples, injection of nucleinic acid, remain inactive. The 

 animals become indolent and tired, begin to suffer with disturbances of coordi- 

 nation and finally die in a coma-like condition. Feeding with thymus gland 

 or injection of it only aggravates the condition. 



