230 SWALE VINCEHT 



observed. Neither did the chronic, progressive cachexia described by 

 Hjofmeister appear in any of the cretins kept alive for/ a year. 



Transfusion of normal blood serum into the cretins had no apparent 

 effect on the condition. Some improvement, however, resulted from trans- 

 fusion of serum from thyroid-fed rabbits. Feeding with desiccated thyroid 

 gland substance markedly ameliorated the symptoms but failed to bring 

 about entirely normal development. Discontinuance of the medication 

 led to relapse. The cretins proved more susceptible than normal rab- 

 bits to the toxic action of thyroid feeding. 



It seems clear from the experiments of Sutherland Simpson and others 

 that in young animals removal of the thyroid (one or more parathyroids 

 being left behind) will bring about a condition resembling .cretinism in the 

 human subject. In older animals symptoms may not be observed, but 

 thickening and dry ness of the integument with a tendency to loss of hair 

 and wasting followed by adiposity have been described. It is stated that 

 there is loss of muscular tone, and that regeneration of tissues is slower 

 than normal. There may be anemia. The body temperature is low; the 

 power of heat regulation is diminished (Lorraine Smith) and the animal 

 becomes poikilothermic (Boldyreff) ; the sexual functions are interfered 

 with. It has been stated that the limit of assimilation of carbohydrates 

 is raised. "The nervous system is markedly affected, dullness and apathy 

 being prominent symptoms. Many nerve-cells, especially those of the 

 cerebral cortex, exhibit a shrunken appearance, and present a strong con- 

 trast with those of the normal animal" (Shafer). A myxedematous con- 

 dition of the -skin" has been described, by some authors, but the present 

 writer has never seen this (vide supra). 



According to Edmunds (&) complete extirpation of thyroid and para- 

 thyroids in dogs is -frequently followed by cataract. 



Thyroidectomy in the amphibia interferes with the normal metamor- 

 phosis, and retards or completely stops growth and ossification of bone. 

 The operation docs not appear to hinder the development of the gonads. 

 (Hoskins, Terry, Allen (a).) 



Several observers have reported a diminution in the alexins and opso- 

 nins in the serum after removal of the thyroid. 



V. Eiselsberg described atheromatous changes in the aorta after 

 thyroidectomy in lambs. 



The Internal Secretion of the Thyroid and Its Nervous 



Mechanism 



It used to bo commonly stated that the internal secretion of the thyroid 

 gland passes, not directly into the blood-stream, but indirectly by means 

 of the lymphatics. Hut more recent investigations have rendered this 

 theory very doubtful (Carlson and Woelfel). 



