YOUTH, that state of man, in which he approaches towards his greatest perfection of body.—— In this state, according to Dr Cullen, rigidity and strength are now greater, but still, with respect to the middle point, laxity prevails; a less proportion of fluids, with respect to the vessels, but still prevailing humidity; increased cellular substance, on which the growth of the body chiefly depends till the acme, and long after; heart less in proportion to the system than formerly, and more in a balance with it; the arteries are diminished, in some measure, with respect to the veins, but still exceed them; the whole viscera are larger, and particularly the lungs; and, as the vessels are more rigid, consequently a greater determination of fluids to that organ, which explains the diseases incident to the stage of life, hæmoptoisis, peripneumony, &c. The same sensibility and irritability continue, perhaps, as before, but the former is more accurate, from the tension of the vessels, and consequently the fibres. The latter is rather increased, and hence irascibility more frequently appears at this period. There is also great mobility, but with much less levity.