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TEXT-BOOK OF PHYSIOLOGY. 



The Parathyroids. The parathyroids are small bodies, usually four in 

 number, two on each side. They are divided into superior and inferior. 

 The superior are situated internally and on the posterior surface in close 

 relation to, and frequently imbedded in, the substance of the thyroid; the 

 inferior are situated externally, sometimes in contact with, and at other 

 times removed a variable distance from the thyroid (Fig. 212). Micro- 

 scopically the parathyroids consist of thick cords of epithelial cells separated 

 by septa of fine connective tissue and surrounded by capillary blood-vessels. 

 Effects of Parathyroid Removal. The surgical removal of the para- 

 thyroids is followed in the course of from two to five days by the death of the 

 animal preceded in most instances by a series of symptoms which are em- 

 braced under the general term "tetany." These symptoms are fibrillary 

 contractions of muscles, tremors, spasmodic contractions and paralyses of 



groups of muscles and not infrequently 

 convulsive seizures and coma. During the 

 convulsion there is an acceleration of the 

 heart-beat, and increase in the respiratory 

 movements which frequently, become dysp- 

 neic in character. There is also a loss 

 of appetite, nausea, mucous vomiting, and 

 diarrhea. Death may occur during a 

 convulsion or from coma. (Morat and 

 Doyon.) 



These results for the most part occur 

 only when all the parathyroids are removed. 

 It is asserted that even if one gland is re- 

 tained the animal does not die. The above 

 described symptoms may manifest them- 

 selves, however, but they are slight in 

 degree. 



Vincent and Jolly have recently pub- 

 lished the results of a series of experiments 

 which seem to negative to some extent the 

 preceding statements. These experiment- 

 ers state that while it is true, that, as a 

 rule, the removal of both thyroids and para- 

 thyroids in the carnivora is a fatal opera- 

 tion, there are nevertheless many excep- 

 tions; and in the mammalia generally, e.g., 



cats, dogs, foxes, guinea-pigs, rats, and monkeys, the exception becomes the 

 rule as more than 51 per cent, of animals survived the operation for a pro- 

 longed period and of these 68 per cent, showed no specific symptoms of any 

 kind. From the contradictory observations it is evident that the subject 

 needs further investigation. 



The Pituitary Body. The pituitary is a small body lodged in the 

 sell a turcica of the sphenoid bone. It measures 14 mm. from side to 

 side, 8 mm. from befcre backward, and 6 mm. from above down, and con- 

 sists of an anterior lobe somewhat pink in color, and a posterior lobe yellow- 

 ish-gray in color. The anterior lobe is much the larger and partly embraces 



FIG. 212. The position of the para 

 thyroid glands. (Zitckerkandl.) 



