THE THYROID APPARATUS 63 



at a greater or less distance from it, are of by no means rare 

 occurrence. Many animals, especially dogs, are not necessarily 

 thyroidless because the thyroid gland has been removed from 

 the neck. After thyroidectomy, cases such as these frequently 

 show only passing symptoms of suppression, or the signs may 

 be absent altogether. 



There is a certain amount of difference between the signs of 

 thyroid suppression in young growing animals and in adults. 

 This difference does not affect the essential character of the 

 changes, the so-called athyrosis, which always involves the 

 metabolic processes of the entire organism. In the case of young 

 individuals, however, the derangement of metabolism is mani- 

 fested with peculiar distinctness in the changes which take place 

 in the processes of growth. 



Hofmeister (1892) found that the extirpation of the thyroid of 

 young rabbits, the external parathyroids being left in situ, was 

 followed by a retardation of growth and the development of a 

 condition of chronic cachexia. 



Further experiment showed that the arrest of growth was 

 due to a remarkable retardation of the process of ossification, 

 both of the epiphyses and of the synchondroses. The long 

 bones, the pelvis and the vertebral column, showed the greatest 

 departure from the normal, the skull the least. The growth of 

 the long bones was retarded to the extent of at least a third of 

 their proper length, and microscopic examination of the epiphysial 

 line showed specific degeneration, consisting in a reduction of 

 normal cell proliferation, combined with vesicular swelling of 

 the cartilage lacunas and shrinkage, or even partial destruction, 

 of the cells. 



In the internal organs, Hofmeister found a condition similar 

 to that described by Rogowitsch in the case of adult rabbits, 

 namely, enlargement of the glandular portion of the hypophysis 

 cerebri, and the appearance of large vacuoles in the protoplasm 

 of the enlarged principal cells. Moreover, he observed a similar 

 formation of vacuoles, together with degenerative changes, in 

 the epithelial cells of the looped uriniferous tubules. The con- 

 dition of the organs of generation was particularly striking. In 

 addition to degenerative changes, the ovaries invariably showed 

 premature maturity of many of the follicles. Jeandelize dis- 

 covered later that, in male animals, there is imperfect development 

 of the testicles. 



v. Eiselsberg found that in sheep whose thyroids had been 

 removed at the age of ten days, there was conspicuous retardation 

 of growth and a change in the mental condition, which forcibly 

 suggested the idiocy of cretinism. Post-mortem examination 

 showed that, in addition to a high degree of derangement of the 

 processes of skeletal growth, there was widespread atheromatous 

 degeneration in the aorta. The intima was covered with very 



