796 PHYSIOLOGY OF DIGESTION AND SECRETION. 



removed these animals die with the symptoms described in the 

 case of dogs, cats, and other carnivorous animals. This result at- 

 tracted attention to the parathyroids. Numerous experiments, 

 especially by Moussu,* Gley,f and Vassale and Generate, t have 

 seemed to show a marked difference between the results of thyroi- 

 dectomy and parathyroidectomy. When the parathyroids alone are 

 removed the animal dies quickly with acute symptoms, muscular 

 convulsions (tetany), etc.; when the thyroids alone are removed 

 the animal may survive for a long period, but develops a condition 

 of chronic malnutrition, a slowly increasing cachexia which may 

 exhibit itself in a condition resembling myxedema in man. This 

 distinction has been generally accepted, and it throws much light 

 upon the discrepancy in the results obtained by some of the earlier 

 observers. Complete thyroidectomy with the acutely fatal results 

 usually described includes those cases in which both thyroids and 

 parathyroids were removed, while probably many of the apparently 

 negative results obtained after excision of the thyroids are expli- 

 cable on the supposition that one or more of the parathyroids were 

 left in the animal. It should be stated, however, that two recent 

 observers, Vincent and Jolly, as the result of numerous experi- 

 ments made upon different varieties of animals, throw some doubt 

 upon these conclusions. They contend that in herbivorous animals 

 fully half of those operated upon survive complete removal of all 

 thyroid tissue, showing no evil symptoms except perhaps a di- 

 minished resistance to infection. Carnivorous animals, on the con- 

 trary, usually die after such an operation. In spite of such con- 

 tradictory results in the hands of some observers the general opinion 

 prevails that complete removal of the parathyroids is followed by 

 acutely toxic results which develop rapidly and the most prom- 

 inent symptom of which is muscular tetany. Several observers 

 have reported that injections of extract of the parathyroids cause 

 this last-named symptom to disappear without, however, protecting 

 the animal from a fatal outcome. The experimental evidence in 

 the case of the parathyroids tends to support the view that their 

 function consists in neutralizing in some way toxic substances 

 formed elsewhere in the body, and that therefore after removal of 

 these glands death occurs from the accumulation of such toxic 

 bodies in the blood and tissues. Thus Macallum states that in 

 animals in which tetany had developed as a consequence of extir- 

 pation of the parathyroids, bleeding and infusion of salt solution 

 caused the tetany to disappear. In a^ interesting case of tetany 



* Moussu, 'Proc. Fourth International Physiolog. Congress," 1898. 

 fGley, " Pfluger's Archiv," 66, 308, 1897. 



j Vassale and Generale, "Archives italiennes de biologie," 33, 1900. 

 ^Macallum, ' ' Centralblatt f. allg. Pathol. u. patholog. Anat. ." 1905, 

 xvi.,'385. 



