In the daily routine of medical work we are called upon to deliver what may come to pass. The constant weighing and measuring of our observations and experience lead us naturally to an estimation of probabilities. Recovery or death—success or failure in the appointed strife with disease—that is the momen tous question to which the physician must endeavour to find an answer. Things have happened; what is to come to pass? Much of skill in prognosis is personal, empirical, and incommunicable; but, as our science advances, with the contributory aid of all the sciences that are subordinate to the master art of healing, so, in just proportion, our premonitions will be determined.