The question how far results obtained with dogs can be applied safely to man may be open to discussion, but we must first be sure of our facts before arguments or conclusions of any kind are warranted. It is to be remembered that dogs are as sensitive in many ways as man, and no physiological experiment covering a long period of time can be carried out with any hope of success unless there is due regard for proper hygienic conditions, some degree of variety in diet, and reasonable opportunities for fresh air and occasional exercise. I fancy that even the most vigorous and hardy man, if confined for six consecutive months in a room just large enough to furnish requisite air-space and to permit of extending his body at full length, would find himself at the end of such a period in a condition far from healthful, even though there were perfect freedom of choice in diet. If, however, there were added to the above conditions monotony in diet extending through many months, there would be no occasion for surprise if the individual lost appetite and strength, and showed signs of disturbance of the gastrointestinal tract

It is doubtful if there is full appreciation of the possible effect of monotony, in the ordinary dietary experiments on dogs. Man quickly feels the effect; the sportsman camping in the woods by brook or lake enjoys his first meal of speckled trout and has no thought of ever becoming tired of such a delicacy; but as trout cooked in various ways continue to be placed before him three times a day, and with perhaps very little else, he soon passes into a frame of mind where salt pork would be a luxury, and where he would prefer to go hungry rather than eat the delicacy, if indeed he has appetite to eat anything. Is it strange that dogs confined in cages barely large enough to permit of their turning around, and fed day after day and month after month with exactly the same amount of desiccated meat, fat, and rice, should show signs and symptoms, if nothing worse, of disturbed nutrition? It is necessary in experiments of this kind that the animals be confined for given periods, at least, since otherwise it would be impossible to determine the extent of nitrogen excretion and the rate of proteid katabolism, etc. It is possible, however, to limit the time of close confinement to, say, ten consecutive days, this to be followed by a like period of comparative freedom, thus insuring opportunities for an abundance of fresh air and exercise.

The experiments of which I wish to speak, and which had for their object a study of the effect of low proteid diet on dogs, as types of high proteid animals, were carried out at our laboratory in the Sheffield Scientific School and were made possible by liberal grants from the Carnegie Institution of Washington, thus providing means for securing the requisite number of chemical assistants. The experiments were conducted on a somewhat large scale, over twenty dogs being made use of, while many of the experiments extended through a full year. The results in their entirety are not yet ready for publication, but I am able to present in a general way observations on six dogs, which will serve as an ample illustration of what may be expected with high proteid animals when living on a low proteid diet under healthful conditions. All of the six dogs whose cases are here presented were fed on a mixed diet, with some fresh meat each day; bread, cracker dust, milk, lard, and rice being the other foods drawn upon to complete the dietary. The animals were fed twice a day, each meal being accurately weighed and of definite chemical composition. A large, light, and airy room, kept scrupulously clean, and in the winter time properly heated by steam, served as their main abiding place. In this room were a suitable number of smaller compartments, the walls of which were composed of open lattice work (of iron), so as not to interfere with light or air, and yet adequate to keep the dogs apart. These compartments were not cages in the ordinary sense, but were truly large and roomy. The entire floor under the dogs was composed of metal, the joints all soldered, the floor being sloped to a metal gutter in front so that all the compartments could be flushed out each morning and kept sweet and clean. In pleasant weather, immediately after their first meal, the dogs were taken out of doors to a large enclosure near by, where they were allowed perfect freedom until about four o'clock, when they were taken in for their second meal (between four and five o'clock in the afternoon). The outdoor enclosure was inaccessible to every one except the holder of the key, and the dogs while there were wholly free from annoyance. Once every month, during a period of ten consecutive days, each dog was confined in the metabolism cage so as to admit of the collection of all excreta, in order to make a determination of the nitrogen balance. Practically, therefore, each dog was in close confinement only one-third of the month, the remaining two-thirds being spent in much more congenial surroundings. I have entered thus fully into a description of the conditions prevailing, because I deem them exceedingly important, and because therein undoubtedly lies the explanation of the striking contrast between our results and those of the earlier investigators of this subject.