THYMUS AND THYROID. 333 



Malpighian corpuscles. They resemble tiny lymphatic 

 glands in structure. 



The Thymus is an organ which only exists in childhood. 

 At birth it is found lying around the windpipe, in the upper 

 part of the chest cavity and the lower part of the neck. It 

 increases in size until the end of the second year, and then 

 begins to dwindle away. It is grayish pink in color, of a 

 soft texture, and, in microscopic structure resembles some- 

 what a lymphatic gland. Hence its function has been sup- 

 posed to be the formation of new lymph corpuscles. The 

 "sweetbread" of butchers is sometimes the pancreas and 

 sometimes the thymus of young animals belly and neck 

 siveetbread. 



The Thyroid Body and the Suprarenal Capsules. 

 The former of these structures lies in the neck on the sides 

 of and below "Adam's apple." It is dark red-brown in 

 color, and sometimes becomes very much enlarged, as in the 

 disease known as goitre. This enlargement appears to be 

 often due to drinking water containing magnesian limestone 

 in solution. In England, for instance, it is known as "Der- 

 byshire neck" from being especially frequent in parts of that 

 county, where the hills are mainly composed of magnesian 

 limestone rocks; and the same geological formation is 

 found in tlu.c districts of Switzerland where cretinism 

 (one of the symptoms of which is an enlarged thyroid 

 body) prevails. When the thyroid is removed from dogs, 

 a great excess of mucus collects in their bodies. It even is. 

 found in the blood, which in lioulth contains none of it. 

 The animals also become idiotic. In human beings 

 disease of the thyroid sometimes causes like symptoms, 

 giving rise to the rare disease named myxodema. 



The suprarenal bodies lie one over the top of each kid- 

 ney. Their use, like that of the thyroid, is quite prob- 

 lematical. In what is known as Addison's disease (in 

 which the skin becomes of a bronze color) it is said that 

 these bodies are altered; but it is probable that the change 

 in them is one of the results or concomitants of the disease, 

 rather than its cause. 



