94o INFLUENCE OF DUCTLESS GLANDS ON METABOLISM. 
with leucocytic infiltration of the cornea. 1 Horsley was the first to 
operate upon monkeys. He found that these animals survive the 
removal of the thyroid much longer than do dogs, and that in them, as 
in man, a " myxedematous " condition gradually supervenes. They 
also pass into a condition which is unmistakably similar to cretinism, 
besides which, as in dogs, they are subject to the supervention of muscular 
tremors. These, however, may be greatly abated, or their onset delayed, 
if the animals are kept in a very warm atmosphere. 
It was further found by Allara 2 and by Ewald 3 that no results are 
obtainable by thyroidectomy in birds (although it is fatal to reptiles), 
and most observers found the same to be the case with rodents and 
herbivora generally. 4 It is a noteworthy fact that in aged dogs thyroid- 
ectomy does not produce the normal symptoms. In man also it is 
found that the supervention of operative myxcedema is less frequent as 
age advances. 5 The absence of the result in birds has never yet been 
satisfactorily explained ; but various attempts have been made to 
explain the frequent absence of result in herbivora. 6 It may be, either 
that a portion of the gland has been left behind, or that the animals 
were not kept under observation for a sufficient time (Horsley), or 
that there existed in the particular case in question accessory thyroids 
and parathyroids, separated from the main body and not removed in 
the operation. This is the explanation which is given by Gley of the 
negative results which usually attend thyroidectomy in rabbits. Gley 
states that if in these animals care be taken to remove the accessory 
structures as well, the usual symptoms supervene and are very rapidly 
fatal. 7 Moreover, he finds that if in young dogs all the parathyroids 
are removed, while the main body of the thyroid is left intact, the 
symptoms which have been regarded as characteristic of complete 
thyroid removal nevertheless supervene, an observation which, if con- 
firmed, shows that it is these structures which are physiologically the 
more important part of the organ. s 
The symptoms which follow thyroidectomy are of two classes — 
nervous and metabolic, although we are not able to say that the 
nervous symptoms are not produced by metabolic changes in the tissues 
of the nervous system ; nor is it certain that the metabolic changes in 
1 Gley and Rothon-Duvigneaud, Arch.' de jihysiol. norm, etpath., Paris, 1894, p. 101. 
2 S'perim.cntalc, Firenze, 1885, p. 281. 
3 Ewald and Rockwell, Arch. f. d. gcs. Physiol., Bonn, 1890, Bd. xlvii. S. 160. 
4 Sanguirico and Oreccliia (abstract in Centralbl. f. Physiol., Leipzig u. AVien, 1887, 
Bd. i. S. 587). 
5 Bourneville and Bricon (Arch, dcncurol., Paris, 1886) have shown that the liability 
to constitutional symptoms usually ceases at about the thirtieth year. 
6 According to Briesacher (Arch./. Physiol. , Leipzig, 1890, S. 509), the character of the food 
in dogs modifies the effects of thyroidectomy. Dogs fed with milk bear the operation better 
than those fed on flesh, nor do they exhibit, as the latter often do, convulsions after a meal. 
7 Compt. rend. Soc. dc biol., Paris, 1891, pp. 841, 843. See also Edmunds, " Proc. Phys. 
Soc," Journ. Physiol., Cambridge and London, 1895, vol. xviii. Hofmeister (Bcitr. z. 
klin. Ghir., Tubingen, 1894, Bd. ii. S. 441), and Leonhardt (Virchows Archiv, 1897, 
Bd. cxlix. S. 341) have also got positive results in rabbits ; and G. R. Murray has succeeded 
in producing symptoms of myxcedema in a rabbit from which he had some time previously 
removed the thyroids (Brit. Med. Journ., London, 1896, vol. i. p. 204). 
8 Gley, Compt. rend. Soc. dc biol., Paris, 1897, p. 181 ; Yassale and Generale, Arch, 
ital. dc biol., Turin, 1895 and 1896, tome xxv. p. 459 ; and tome xxvi. p. 61 ; Edmunds, 
"Proc. Phys. Soc," Journ. Physiol., Cambridge and London. 1896, vol. xx. ; also Trans. 
Path. Soc. London. 1S95, 1896, and Journ. Path, and Bacteriol., Edin. and London, 
1896, vol. iii. p. 488. Blumenreich and Jacoby (Bcrl. klin. JVchnschr., 1896, S. 327) state, 
on the other hand, that the inclusion or exclusion of parathyroids is immaterial to the 
result of thyroidectomy (but cf. Gley, Arch. f. d. cjcs. Physiol., Bonn, Bd. lxvi. S. 308). 
