RE LA TIVE AC Til VTY OF DICES TI VE SOL UTLONS. 3 2 5 
of 19 c.o. of water and 1 c.c of glycerin-carmine solution. In this manner 
ten standard tints are obtained, the values of which correspond to the numbers 
1 to 10; these are mounted in a stand against a uniform white background, 
and are used to compare with the results of digestion, after equal intervals 
of time. For example, if after thirty minutes' digestion the tint of one test 
tube corresponds most closely to that of Standard 2, while that of another 
corresponds to Standard 6, the latter is three times as powerful a digestive 
solution as the former. The digestive solutions should be so diluted that they 
act somewhat slowly, because after a time a maximum tint obtains, and then 
the weaker digestive fluid catches up on the other ; the farther apart from 
this maximum the measurements are taken the better. Also, if a close approxi- 
mation to the comparative /nun//,//* of pepsin in two solutions is required, 
after a preliminary experiment the stronger of the two must be diluted 
experimentally until its action is equal to that of the other, then the pro- 
portion of dilution gives the proportionate strength in pepsin of the two 
solutions. This determination may be most speedily attained by making a 
simultaneous series of dilutions of the stronger solution, and comparing the 
strength of their action with that of the other solution or a series made 
from it. 
Two tubes of equal speed of action are picked out, and from their dilutions 
the comparative richness in pepsin of the original fluid easily follows. Griitzner's 
method may also be employed without a scale of standard tints, by stopping 
digestion after an equal period, and then diluting the stronger solution until 
its tint becomes equal to that of the weaker, or by carrying out two series 
in aliquot dilution of the two solutions to be compared, and picking out 
equally advanced members of the two series. In case the comparison is made 
with solutions of unequal power, it must be remembered that what is measured 
is the comparative digestive power and not the comparative strength of the 
solutions in pepsin, because the two are not proportional ; l in all cases it is 
preferable, for accuracy, to prepare solutions from the originals of equal power, 
and from the amount of dilutions of these to deduce the comparative strength 
in pepsin of the originals, as indicated above. 
Mette's method. 2 — This method is stated by Samojloff to yield exact 
results. It consists in filling fine glass tubes of 1 to 2 mm. in diameter with 
fluid Avhite of egg, then coagulating by heat, and cutting off pieces of equal 
length. These are placed in the digestive solutions at body temperature, and, 
after the lapse of a certain interval, the length of white of egg digested off is 
measured, which gives a measure for the comparative activities of the two 
fluids. 
Griitzner s has also introduced methods for comparing the diastatic 
and fat-splitting powers of pancreatic extracts. 
That for diastatic action closely resembles Griinhagen's method for proteo- 
lytic action. Equal volumes of 3-4 per cent, starch paste are placed on similar 
filters, through which they do not filter until dissolved ; to each filter 02 to 
0*3 c.c of the extracts to be compared are next added, when solution of the 
starch takes place at a rate proportional to the amount of enzyme present, 
and a comparison of the amounts filtering through in a given time supplies 
a measure for the activities of the extracts. 
The method of comparing the fat-splitting powers of different extracts 
consists in allowing the extracts to act on an emulsion in presence of litmus, 
and noticing the time and amount to which the latter is turned red by the 
acid developed. The emulsion recommended is made by mixing 10 parts of 
1 See Schlitz's law, p. 322. 
2 Samojloff, Arch, de sc. biol., St. Petersbourg, 1893, tome ii. p. 707. 
s Areh.f. d. ges. Physiol., Bonn, 1876, Bd. xii. S. 293, 303. 
