72 THE THYROID AND 



shows a sequence of changes remarkably like those 

 occurring in exophthalmic goitre, namely, distention 

 and irregular shape of the vesicles, with watery fluid 

 instead of colloid, and columnar epithelium instead 

 of cubical. 



REMOVAL OF PARATHYROIDS. 

 The variation in the sj^mptom-complex following 

 on thyroidectomy, and the variabiUty of response 

 to thyroid feeding, both depend on any coincident 

 injury to the parathjToid glands. For many years 

 these glands passed unrecognized, and most of the 

 effects attributed above to removal of the thyroid 

 are as a matter of fact due to loss of the parathyroids. 

 These are two pairs of small glands, about one-third 

 of an inch long and usually flattened in shape, l}ing 

 behind the lateral lobes of the thyroid close to the 

 trachea, not easily distinguishable from the thyroid 

 except by the microscope, when they are seen to 

 consist of columns of polygonal cells with no regular 

 arrangement into acini, and secreting no colloid. 

 One pair was discovered by Sandstrom in 1880, 

 and the functions were investigated by Gley in 

 1892 ; but the second pair was not recognized till 

 Kohn's monograph appeared in 1895. A number of 

 physiologists have since described the effects of 

 removal (VassaH and GeneraU, Edmunds, Moussu). 

 If all four parathyroids are taken away, the animal 

 succumbs rapidly, with symptoms just such as have 

 been described under the heading of th>Toidectomy, 

 tetany being a marked feature. The signs are the 

 same whether the thyroid gland is removed or left. 



