552 SUTHEKLAND SIMPSON 



glands contained such a high percentage of iodin much more than any 

 other organ in the body he concluded that they belong to the same sys- 

 tem functionally the "thyroid system of organs." Subsequent research 

 has not given support to Gley in this matter. 



In the literature Mendel is frequently cited as having found more 

 iodin in the parathyroids than in the thyroid in the human subject, both 

 relatively and absolutely, but in this he is misquoted, as his statement 

 refers to accessory thyroids, which are occasionally found, and not to the 

 parathyroids. 



Chenu and Morel in 1904 repeated the analyses of Gley in dogs, rab- 

 bits, and chickens, using the Baumann method. They separated com- 

 pletely the external parathyroids from all surrounding tissue, dried them 

 on filter paper, and, at the same time, took from the same animal, re- 

 recently killed, a small portion of the thyroid equal to the combined 

 weights of the external parathyroids. With the colorimeter they were able 

 to detect iodin to 0.0025 milligram, and in the parathyroids of no single 

 animal was it equal to this amount, although in the same weight of thyroid 

 it could be estimated, as a rule. In the chicken, for example, while the 

 iodin in the parathyroids was less than 0.0025 milligram, and its exact 

 quantity could not be determined, in an equal amount of thyroid tissue it 

 was 0.0110 milligram and 0.0140 milligram, respectively, in the two 

 analyses given. 



That the parathyroids, like other organs, do contain traces of iodin, if 

 a sufficient quantity of the tissue be secured, they showed by collecting 

 these glands from eight dogs (0.133 gram) for a single analysis. One 

 gram of fresh dog parathyroid they found by calculation would contain 

 0.0503 milligram of iodin, which for each animal would be only a trace 

 less than the method was capable of indicating. 



Later workers have corroborated Chenu and Morel. Estes and Cecil 

 carried out a similar investigation in dogs, cows, horses, sheep, and man, 

 not taking the glands from a single animal, but collecting a number from 

 several of the same species, in order to obtain a sufficient amount of mate- 

 rial for analysis. Baumann's method was employed, choloroform being 

 used instead of carbon clisulphid for the colorimetric test, and with this, 

 iodin to the amount of 0.0025 milligram could be detected. In the dog 

 0.25 grain and 0.24 gram of dried parathyroid two estimation yield- 

 ed only infinitesimal amounts of iodin. In the cow (when as much as 

 0.5 grain of dried parathyroid was used for a single analysis), horse, 

 sheep, and man the results were always negative, except in one case, in 

 which 3.78 grams of dried horse parathyroid yielded 0.06 milligram of 

 iodin. Two other analyses from the horse gave negative results. Estes 

 and Cecil call attention to the fact that in the dog and other carnivorous 

 animals, in which the two organs are intimately associated anatomically, it 

 is hardly possible to be certain that no thyroid tissue has adhered to the 



