As regards the age of patients, he showed by calculation that typhoid usually attacked much younger patients than typhus, the average age of his cases of the one being 22 years, of the other 42 years. In typhus, death took place on the average on the fourteenth day, while in typhoid the average was the thirty-second day of residence in the hospital. The rose rash of typhoid, disappearing completely on pressure, resuming the original appearance on the withdrawal of pressure, was clearly discriminated from the mulberry rash of typhus. His _post mortem_ observations may be considered to have given the death-blow to the idea that typhoid was merely typhus fever with abdominal complications. In closing the series of papers (April 1850) Dr. Jenner remarked, as to the suggestion that he had drawn general conclusions from a too limited number of facts, “A few facts, impartially observed, minutely recorded, and carefully analysed, are, I believe, more likely to give correct results than a multitude of general observations; and moreover, I believe most men would be astonished if they had in numbers all the cases of any given disease they had ever seen, yet concerning which they have generalised. The method I have adopted—however prolix it may be, however difficult to conform to, however tedious the details into which it leads—has this advantage, that if the observer be honest, and capable of noting what is before him, thinking men may judge of the value of his facts, the force of his reasoning, and the correctness of his conclusion; whereas general observations, while they are totally incapable of proving anything, are exposed to all the fallacies of definite statements, because the one, like the other, rests ultimately on the accuracy of the facts observed. If the observations on which any reasoning is founded be erroneous, no cloaking of those observations in general terms can render the conclusions correct. It has been objected to definite numerical statements that they mislead the reader by an _appearance_ of accuracy in cases where there has been great inaccuracy in observation. This objection appears to me to lie against the condition of the reader’s mind, and not against the method.... The more complicated the problem to be solved, the more careful ought we to be that _every_ step in its solution is made correctly. How complex questions, such as arise in medicine, are to be determined mentally—_i.e._, without the aid of figures—by ordinary men, I am at a loss to conceive. Yet physicians think to solve, by mental reveries, problems in comparison with which the most difficult that the most renowned calculators ever answered were child’s play; and not only do they think to solve these problems, but to carry in their minds for years the complicated materials by which they are to be solved.”