somehow or other, but then I will undertake to say that I forgot it all a week afterwards.  Not one trace of a knowledge of drugs has remained in my memory from that time to this; and really, as a matter of common sense, I cannot understand the arguments for obliging a medical man to know all about drugs and where they come from.  Why not make him belong to the Iron and Steel Institute, and learn something about cutlery, because he uses knives?

[Footnote 1:  It will, I hope, be understood that I do not include Therapeutics under this head.]

But do not suppose that, after all these deductions, there would not be ample room for your activity.  Let us count up what we have left.  I suppose all the time for medical education that can be hoped for is, at the outside, about four years.  Well, what have you to master in those four years upon my supposition?  Physics applied to physiology; chemistry applied to physiology; physiology; anatomy; surgery; medicine (including therapeutics); obstetrics; hygiene; and medical jurisprudence—­nine subjects for four years!  And when you consider what those subjects are, and that the acquisition of anything beyond the rudiments of any one of them may tax the energies of a lifetime, I think that even those energies which you young gentlemen have been displaying for the last hour or two might be taxed to keep you thoroughly up to what is wanted for your medical career.

I entertain a very strong conviction that any one who adds to medical education one iota or tittle beyond what is absolutely necessary, is guilty of a very grave offence.  Gentlemen, it will depend upon the knowledge that you happen to possess,—­upon your means of applying it within your own field of action,—­whether the bills of mortality of your district are increased or diminished; and that, gentlemen, is a very serious consideration indeed.  And, under those circumstances, the subjects with which you have to deal being so difficult, their extent so enormous, and the time at your disposal so limited, I could not feel my conscience easy if I did not, on such an occasion as this, raise a protest against employing your energies upon the acquisition of any knowledge which may not be absolutely needed in your future career.

IV.

YEAST.

IT has been known, from time immemorial, that the sweet liquids which may be obtained by expressing the juices of the fruits and stems of various plants, or by steeping malted barley in hot water, or by mixing honey with water—­are liable to undergo a series of very singular changes, if freely exposed to the air and left to themselves, in warm weather.  However clear and pellucid the liquid may have been when first prepared, however carefully it may have been freed, by straining and filtration, from even the finest visible impurities, it will not remain clear.  After a time it will become cloudy and turbid; little bubbles will be seen rising to the surface, and their abundance will increase until the liquid hisses as if it were simmering on the fire.  By degrees, some of the solid particles which produce the turbidity of the liquid collect at its surface into a scum, which is blown up by the emerging air-bubbles into a thick, foamy froth.  Another moiety sinks to the bottom, and accumulates as a muddy sediment, or “lees.”