The physician should be of tender disposition, of wise and gentle nature, and more especially an acute observer, capable of benefiting everyone by accurate diagnoses, that is to say, by rapid deduction of the unknown from the known. And no physician can be of tender disposition if he fails to recognize the nobility of man; nor of philo­sophical nature unless he knows Logic, nor an acute observer unless he be strengthened by God's guidance; and he who is not an acute observer will not arrive at a correct under­standing of the cause of any ailment, for he must form his opinion from the pulse, which has a systole, a diastole, and a pause between these two movements.

Now here there is a difference of opinion amongst physicians, one school maintaining that it is impossible by palpation to gauge the movement of contraction; but that most accomplished of the moderns, that talented man Abú 'Alí al-Ḥusayn b. 'Abdu'lláh Síná (Avicenna),*

says in his book the Qánún that the movement of contraction also can be gauged, though with difficulty, in thin subjects;*

and that the pulse is of two sorts, each of which is divided into three subordinate varieties, namely, its two extremes and its mean; but, unless the Divine guidance assist the physician in his search for the truth, his thought will not hit the mark. So also the examination of the urine, and the observing of its colour and peculiarities, and the deducing somewhat from each colour, is no easy matter; for these deductions are dependent on Divine help and Heavenly guidance; and this is the quality which we have already mentioned under the name of acumen. And unless the physician knows Logic, and understands the meaning of species and genus, he cannot discriminate between that which appertains to the category and that which is peculiar to the individual, and so will not recognize the cause of the disease. And, failing to recognize the cause, he will not succeed in his treatment. But let us now give an illustration, so that it may be known that it is as we say. Disease*

is the genus; fever, cold, headache, dizziness, scarlet fever, and jaundice are the species, each of which is distinguished from the others by a diagnostic sign, while each itself is again divisible into varieties. For instance, ‘Fever’ is the genus, wherein quotidian, tertian, double tertian, quartan, and the sub-varieties of each, are dis­tinguished from each other by a special diagnostic sign, so that, for instance, quotidian is distinguished from other fevers by the fact that the longest period thereof is a day and a night, and that in it there is no rigor, heaviness, lassitude, nor pain.*

Again, inflammatory fever*

is dis­tinguished from other fevers by this, that when it lays hold of anyone it does not abate for several days; while tertian is distinguished by the fact that it comes one day and not the next; and double tertian by this, that one day it comes with a higher temperature and a shorter interval, and another day in a milder form with a longer interval; while, lastly, quartan is distinguished by this, that for two days it does not come and the third day it comes.

Each of these, again, comprises several varieties, and each of these in turn sundry sub-varieties; and if the physician be versed in Logic and possessed of acumen, he will know which fever it is, what the materies morbi is, and whether it is simple or compound, and he can then at once proceed to treat it; but if he fail to recognize the disease, then let him turn to God and seek help from Him; and so likewise, if he fail in his treatment, let him have recourse to God, seeing that the issue is in His hands.