I.—PHYSIOLOGY. {Tay 
Is the same return to synthetic conceptions to be found as a result 
_ of analyses of the biochemist? His work has brought much simplifi- 
4 eation to our notions of the chemistry of the body. We have learned 
that in the exchanges within the living cell we are not necessarily, or 
indeed probably, dealing with molecules of a complexity unknown 
outside the living body; we do not now think as formerly of substances 
being worked up through successive stages of elaboration into a living 
molecule—a molecule of ‘ protoplasm’ of mystical complexity—or of 
other substances reappearing as the result of incessant degradation of 
parts of the living molecule. Analysis has shown already that many 
characteristic cell-changes turn upon relatively simple reactions of a 
_ kind familiar in chemistry between known and relatively simple sub- 
stances. How much further will this analysis proceed? No doubt 
many of the typical functions of particular kinds of cell will become 
expressible in a set of chemical formule, and every simplification 
attained by the biochemist in terms of known chemical or physical law 
will be a notable gain. Yet even now we can feel assured that the 
analyses of the biochemist bring with them new emphasis upon the 
essential unity of the whole organism. Let me give but one illustra- 
tion of this. In the studies of immunity from disease it had long been 
known that substances which to a chemist would appear to be identical 
could be sharply distinguished in the most decisive way by biological 
reactions. Tiny fragments of a small blood-clot can be made thus to 
declare whether they come from a man or from what other animal, 
when no chemist would have dreamed of finding-a distinction. Dudley 
and Woodman have lately been able, however, to bring biochemistry 
within the range of this biological delicacy of discrimination, and have 
_ shown a subtle difference in the chemical architectures of the caseins 
derived respectively from the milk of a cow and of a sheep. More 
recently the two modes of analysis have been brought side by side. 
_ Similar cells in similar organs of the two not widely dissimilar birds, 
the hen and the duck, secrete layers of egg-albumin during the com- 
pletion of that wonderful structure, the egg. From the ‘ white’ of each 
egg can be prepared apparently identical albumins, and in a pure 
crystalline form. ‘This albumin is built up in each case from simple 
materials—amino-acids—derived from the food, and we should naturally 
expect a close similarity between the two kinds of resulting albumin, 
_ that in the hen’s egg and that in the duck’s. The most refined methods 
_ of ordinary chemical examination show us, indeed, that the two are 
chemically identical and indistinguishable, containing on analysis the 
“same amounts of the same varieties of amino-acids. But Dakin has 
lately succeeded in tracing a difference between the two albumins, 
exhibited only as partial differences in the order or pattern in which 
some of the constituent amino-acids are linked together in the structure 
of the albumin molecule. By using a physiological test, Dale, at the 
same time, has been able to show a decisive and even dramatic differ- 
ence between the qualities of the two albumins so near to chemical 
‘identity. By using the ‘anaphylactic ’ reaction of the organic tissue 
from an animal ‘ sensitised ’ against hen albumin, he has found that a 
suitable application of hen egg-albumin will produce a decisive response, 
1921 M 
