8 



Prof. Victor Horsley. 



[Jan. 7, 



perature of 90° F.,* and when they exhibited any nerve symptoms, i.e., 

 tremors, &c, were placed in a hot-air bath at a temperature of 105° F. 

 The effect of this has been to lengthen the duration of life (in all but 

 very young animals) four or five times the extent of that observed in 

 the first series. Instead of living four to seven weeks they now live 

 as many months. At the same time several additional facts of im- 

 portance are noted, and the symptoms before referred to are so modi- 

 fied as to require the addition of a third stage to the two I described 

 in 1884. (These observations refer solely to monkeys.) The animals 

 kept under the extra high temperature above noted thus pass through 

 three stages — (1) neurotic, (2) mncinoid, (3) atrophic. I have said 

 that the neurotic stage under these circumstances may be scarcely 

 marked, or if the nerve symptoms occur, and the animal be put in the 

 hot-air bath, they soon disappear. Next the animal lives through the 

 mucinoid stage, i.e., myxcedematous condition, and arrives in the third 

 stage — the atrophic. Now, the symptoms of the second stage are 

 just as much subdued as those of the first, there is no excessive secre- 

 tion of mucus, the parotid glands do not swell, and the post-mortem 

 examination does not reveal the extensive mucinoid degeneration 

 observed in the first series. Finally, the third, atrophic, stage into 

 which the animal passes is evidenced by great emaciation, functional 

 paresis and paralysis, imbecility, falling blood pressure and tempera- 

 ture, with death by coma. 



I am disposed to regard this fact of the animals passing through 

 these neurotic, mucinoid stages, and dying at the end of the atrophic, 

 as the key to the observation that cretins in whom the thyroid gland 

 is very slowly destroyed, and very chronic cases of myxcedema, do not 

 exhibit much mucinoid degeneration. 



(2.) I will now briefly enumerate the direct effect of the fall of nutri- 

 tion produced by the loss of the thyroid gland on the nerve-centres : 

 (a) Effect on cortex.f The tetanus obtained by stimulating the cortex is 

 remarkably changed (even as soon as one day after the thyroidectomy 

 in a dog, who exhibited violent symptoms in twenty-four hours) by 

 the fact of the fall (when the current was shut off) being as sudden 

 as that observed on stimulating the corona radiata. Next, that the 

 tetanus in a more advanced case is soon exhausted, the curve 

 approaching the abscissa soon after the initial rise ; at the same time 

 the curve is followed by clonic epileptoid spasms, which, however, are 

 soon exhausted. Stimulation of the corona radiata and spinal cord 

 also gave the customary tetanus, which, like that of the cortex, was 

 rapidly exhausted. These stimulations of the nerve-centres sap- 



* In my first experiments (1884) the animals were kept at a temperature varying 

 from 60° to 70° F. 



f G-raphica'ly recorded according to method described by Prof. Schafer and 

 myself (" Proc. Roy. Soc," vol. 39, p. 404). 



