1 1 6 Schunck . — The Chemistry of Chlorophyll. 
My object in referring here to the subject of chlorophyll in 
animals is to impress on physiologists the desirability of not 
resting satisfied with a mere superficial examination of any 
colouring matter supposed to be chlorophyll. In order to be 
decisive the requisite experiments need not be many, nor do 
they require a great amount of material to work on. In 
doubtful cases I would recommend the following method : — 
A moderately strong solution of the colouring matter having 
been obtained, compare its absorption-spectrum with that of 
chlorophyll. After the addition of a few drops of hydrochloric 
acid to some of the solution contained in a test tube, compare 
the spectrum, if changed, with that of acidified chlorophyll. 
Then add some acid to a larger quantity of the solution, and 
allow to stand for several days ; filter off the dark-coloured 
deposit which will have formed — provided chlorophyll was 
present and the solution was sufficiently strong — and dissolve 
some of it in ether, then compare the spectrum of the solution 
with that of phyllocyanin (Fig. 4 of Plate). Dissolve the rest 
of the deposit or part of it in hot alkaline lye, add an excess 
of acetic acid, shake up with ether so as to dissolve the floccu- 
lent precipitate, and allow to stand for several days, after which 
the solution should show the peculiar spectrum of the substance 
produced by the action first of alkali and then of acid on phyl- 
locyanin (see Fig. 11 of Plate). If these four spectra are 
distinctly seen and identified, the colouring matter under 
examination is certainly chlorophyll. 
Chemical Constitution and Functions of 
Chlorophyll. 
Considering the present defective state of our knowledge of 
chlorophyll as a chemical individual, considering how little we 
actually know of its properties and composition, it may appear 
somewhat premature to indulge in speculations as to its con- 
stitution and functions, — but to one who has worked long at 
the subject the temptation to do so is almost irresistible. 
Without entering on the question of the functions of chloro- 
