1880.] On the Chemical Composition of Aleur one- Grains. 387 



plane which contains the axis of rotation) to any required distance 

 from the axis. The two arms meet each other at an angle of 45°. 



From the form and arrangement of the internal pools (see fig. 1) 

 it is evident that whenever the screw e is in contact with any of the 

 pools b, b, b. b, the screw / must be in contact with the pools a, a, a, a 

 (see fig. 2), and further inasmuch as / is nearer the axis than e, the 

 times at which e makes and breaks contact with the pool b must 

 respectively precede and follow those at which contact with the pool 

 a is made and broken by /. Consequently the time during which 

 both are in contact (i.e., during which the circuit Gr G' is closed) is 

 determined solely by the duration of the immersion of /, and can be 

 varied by altering its distance from the centre. 



When it is desired to use the rheotome for investigating the effects 

 of series of excitations recurring at short intervals (tetanus of muscle 

 or nerve), all the pools are equally filled with mercury. 



Their equality must be tested by interpolating each set of pools in 

 the circuit of a Grove's cell, which also includes a recording chrono- 

 graph ; if the chronographic record shows that the durations of the 

 contacts are not perfectly equal, the error must be corrected by adding- 

 or subtracting mercury. For investigating the effects of single 

 excitations, only one of the external and one couple of the internal 

 pools are used. 



The drawing (fig. 2) shows the arrangement of the apparatus as 

 used in the investigations made by Mr. Page and myself of the elec- 

 trical phenomena of the ventricle of the heart of the frog. The 

 instrument is set so that the external contact g is broken at a moment 

 which immediately precedes the immersion of / : consequently the 

 galvanometer circuit G G' is open at the moment of excitation, but 

 closed immediately after, remaining closed so long as / is immersed. 

 By means of the tangent screw, the interval between the opening of 

 the exciting circuit B B', and the closing of the galvanometer circuit 

 G G can be varied at will. 



III. "On the Chemical Composition of Aleurone-Grains." By S. 

 H. Vines, M.A., D.Sc, Fellow of Christ's College, Cam- 

 bridge. Communicated by Michael Foster, M.D., Pre- 

 lector of Physiology in Trinity College, Cambridge. Re- 

 ceived April 1, 1880. 



In a former communication (" Proc. Roy. Soc," vol. 28, p. 218) 

 I gave an account of an investigation of the aleurone-grains of the 

 blue lupin. The following is an abstract of the results arrived at 

 by the investigation of the grains of some other seeds by the same 

 methods : — 



