158 Proceedings of Royal Society of Edinburgh. [sess. 
Various methods of determining the strength of action of the 
suprarenal preparations have been proposed. 
A. — Chemical. 
Colorimetric methods were suggested by Battelli* and others. 
The reactions depend on the rose colour given with a weak 
solution of iodine and on the green tint produced with ferric 
chloride. The nature of these reactions is little understood, and 
the possibility of their being given by other substances is great. 
They do not necessarily afford a reliable test of the physio- 
logical activity of the product. I find that, while they afford a 
means of roughly standardising preparations of greater strength 
than adrenalin 1 in 40,000, it is impossible to use them in more 
dilute solutions. An additional difficulty is presented when the 
solution to be tested is already of a brownish colour. Hence they 
do not seem to afford a reliable or delicate method for standardising 
preparations. 
B. — Physiological. 
1. Perfusion of Vessels of Frog. — Lawen t perfused the frog’s 
vessels and got a decided constriction with 0-002 mg. of suprarenin 
in 10 c.cm. (0*2 per million) under a pressure of 20 cm. of water. 
2. Action on Pupil of Frog's Eye. — Ehrmann, as a preliminary 
to his investigation as to the fate of adrenalin in the blood, devised 
a method of standardising the solutions by their effect on the pupil 
of the frog’s eye. To eliminate the sympathetic effect, he used 
enucleated bulbs. The controls were placed in physiological salt 
solution. The amount of dilatation of the pupil is expressed as 
“maximal,” “almost maximal,” “considerable” and “slight.” He 
showed that 0’00005 mg. in 1 c.cm. (-05 per million) gave a slight 
dilatation of the pupil, while further dilutions gave no result. 
On repeating these experiments of Ehrmann, similarly satisfactory 
results were not obtained. There is difficulty in measuring the 
exact amount of dilatation of the pupil. It is also possible that 
absorption through a fibrous membrane, especially under artificial 
conditions, may not be equal and constant. In one experiment, 
where the solution used was -00025 mg. in ’5 cm. (0*5 per million), 
* Compt. Rend. Soc. de Biolog. , 1902, p. 571. 
t Arch. f. Experim. Path. u. Pharmak., Bd. li. , S. 415. 
