Cogan likewise makes some interesting statements regarding the effects of custom on the consumption of proteid food, especially meats. Quoting further from this author: "The fourth thing that is to be considered in meats is custome. Which is of such force in man's bodie both in sicknesse and in health, that it countervaileth nature itselfe, and is therefore called of Galen in sundry places, an other nature. Whereof he giveth a notable example, where he sheweth that an olde woman of Athens used a long time, in cate Hemlocke (which is a ranke poison) first a little quantitie, and afterwarde more, till at length she could eate so much without hurt as would presently poison another.

... So that custome in processe of time may alter nature." Finally, we may quote one last saying of Cogan's, because of the good sense and wisdom displayed in the sentiment, as true to-day as when it was written more than three hundred years ago: "Neither is it good for any man that is in perfect health, to observe any custome in dyet precisely, as AmolduB teacheth upon the same verses in these wordes: Every man should so order himselfe, that he might be able to suffer beate and cold, and all motions, and meats necessary, so as he might change the houres of sleeping and waking, and his dwelling and lodging without harme: which thing may be done if we be not too precise in keeping custome, but otherwise use things unwonted. Which sentence of Arnoldus agraeth verie well to that of Cornelius Celsus: He that is sound and in good health, and at libertie, should bind himselfe to no rules of dyet. To need neither Phisition or Chirurgion, he must use a diverse order of life, and be sometimes in the countrie, sometime in the towne, sometimes hunt, and sometime hawke. But some man may demand of me how this may agree with that saying of the scholar of Salernus 'if you would be free from physicians, let these three be your physician, a cheerful mind, rest, and a moderate diet.' Whereunto I answer, that a moderate dyet is alwaies good, but not a precise dyet: for a moderate diet is, as Terence speaketh in Andria: To take nothing too much: which alwaies is to be observed. But if a man accustome himselfe to such meats and drinks as at length will breed some inconvenience in his bodie, or to sleepe or to watch, or any other thing concerning the order of his life, such custome must naedes be amended and changed, yet with good discretion, and not upon the sudden: because sudden changes bring harme and weaknesse, as Hippocrates teacheth. He therefore that will alter any custome in dyet rightly, must do it with three conditions, which are expressed by Hippocrates. Change is profitable, if it be rightly used, that is, if it be done in the time of health, and at leisure, and not upon the sudden."

This noteworthy book written by Cogan was preceded by the writings of Louis Cornaro, the Venetian, who forty years before had published the first edition of his celebrated book, "The Temperate Life," and who was a most ardent advocate of the benefits to be derived by living temperately, especially in matters of diet. The simple diet which served for the nourishment of the oldest peoples of Syria, Greece, Egypt, and of the Romans when they were at the height of their prosperity and culture, was advocated by Cornaro as conducing to longevity, better health, and greater comfort of mind and body. Himself a striking example of the effects of a reasonable abstinence in diet (the last edition of his book having been written at the age of ninety-five), his teachings have continued to attract attention down to the present day; and although we have no values in grams or calories expressive of his average food consumption, it is quite evident that Cornaro lived a very abstemious life, eating little of the heavier articles of diet common to his time and country. It is perhaps not strictly physiological to refer to these cases, yet they have value as representing a sentiment, common to the centuries now passed, that benefit was to be derived by mankind from greater care in the taking of food; that prevalent customs and habits were leading the people into intemperate modes of life, and that these were surely tending toward the physical and mental deterioration of the nation. We may attach much or little weight to these conclusions, but there is a certain degree of significance in the views, current then as now, that dietetic customs and habits have no real connection with bodily requirements.

Passing down to our own times, we find physiologists, by the aid of scientific methods, studying the effects of smaller amounts of food (smaller than custom prescribes) on the condition of the body, thereby evincing a certain degree of skepticism concerning the dietary standards based on habit and usage. This has been especially true regarding the nitrogen requirement, or the need for proteid food. As has been clearly pointed out in other connections, there are two distinct needs which the body has for food; one for proteid or nitrogen, the other for energy-yielding material. According to the Voit standard, a man of average body-weight doing a moderate amount of work requires daily 118 grams of pro-teid food, or about 16 grams of metabolizable nitrogen, with fat and carbohydrate sufficient to yield a total fuel value of over 8000 large calories. As we have seen, the fuel value of the food must of necessity be a variable quantity because of variations in bodily activity. The more muscular work performed, the greater must be the intake of carbohydrate and fat, if the body is to be kept in equilibrium. With proteid or nitrogen, however, the case is quite different, since with adequate amounts of non-nitrogenous food, proteid is not drawn upon for the energy of muscular work. We can conceive of the nitrogen requirement, therefore, as being a constant factor in the well-nourished individual and dependent primarily upon body-weight, or more exactly, upon the weight of true proteid-containing tissue. Obviously, whatever else happens, there must be enough proteid food taken daily to maintain the body in nitrogen equilibrium. If this can be accomplished only by the ingestion of 16 grams of metabolizable nitrogen, then it is plain that the daily ration must contain at least 118 grams of proteid food; t. e., it must conform approximately at least to ordinary usage.