42 Rev. S. Haughton on the Law of Fatigue, [Nov. 18, 



From these it is gathered that sodium vanadate causes — 



(1) A diminution of blood-pressure which is not continuous, 

 but intermits during the operation of the poison ; 



(2) A disappearance of respiration-curves ; 



(3) A diminution and irregularity of pulse, which is also inter- 

 mittent. 



The results are discussed and considered to be due to an action 

 of the poison on the vaso-motor centre and on the intracardiac 

 nervous mechanism, 

 (iv) On the function of respiration. Subcutaneous or venous injec- 

 tion was again employed in the cases of seven rabbits, normal or 

 with divided vagi. The results show that sodium vanadate causes — 



(1) A stimulation, followed by 



(2) A depression, of respiration, the latter being not continuous 

 but intermittent ; they are discussed and considered to be due to 

 an action of the poison upon the respiratory nervous centre. 



(v) On the functions of muscle and nerve. Subcutaneous injection 

 was employed in the nineteen experiments described, which were 

 performed on frogs, guineapigs, and rabbits. Tables are inserted 

 illustrating diagram matically the action of the salt. The results of 

 these experiments are found to be the same as those given under 

 A, where the general symptoms of poisoning by sodium vana- 

 date are enumerated; and it is concluded, from the facts here 

 stated, that the cause of the nervous symptoms is an action of the 

 vanadate upon the central system of the spinal cord and medulla 

 oblongata, and not upon nerve-trunks of peripheral terminations 

 or upon muscle. 

 In the fourth section the chief results of the research are gathered 

 up and briefly enumerated. 



III. "On some Elementary Principles in Animal Mechanics. 

 No. VII. The Law of Fatigue." By the Rev. Samuel 

 Haughton, M.D. (Dubl.), D.C.L. (Oxon.), F.R.S., Fellow of 

 Trinity College, Dublin. Received June 21, 1875. 



The approximate law of muscular action, which I have called the law 

 of fatigue, is thus expressed : — " When the same muscle (or group of 

 muscles) is kept in constant action until fatigue sets in, the total work done 

 multiplied by the rate of work is constant." 



The following experiments, in illustration of this law, were performed 

 in Trinity College during the spring of the present year. 



I instructed a number of medical students, chosen at random, to raise 

 dumbbells of varying weight, one in each hand, in the tranverse plane, 

 with hands supinated, raising and lowering the weights in equal times 

 regulated by the beat of a pendulum. This process was continued until 



