The noticeable increase in metabolism found by the earlier investigators as a result of the ingestion of flesh led to tests on animals to determine the influence of extracts which consist chiefly of creatine and its allied compounds. Experiments with man on this subject are extremely limited in number. Beef extract (probably 15 per cent water) in amounts of 12 to 18 grams per day was used in some of the classical experiments of Pettenkofer and Voit1 on their so-called fasting days, but as no suitable basal value is available for comparison the results of the experiments give no evidence as to the possible effect of the extract upon the metabolism. In our study on the influence of the ingestion of food, a study was also made of the effect of ingesting beef tea.

Statistics Of Experiments

The series of experiments on beef tea included five experiments with the respiration calorimeter at Middletown (see tables 88 to 92) and two experiments with the chair calorimeter at Boston (see tables 93 and 94). In addition, six experiments were made with the universal respiration apparatus in Boston (see tables 95 to 100). The results of these experiments are summarized in tables 67 and 68. (See pages 135 and 136).

For the calorimeter experiments the beef tea was made by extracting fresh beef with water; in all but one of the respiration experiments it was prepared from a so-called extract of beef, a commercial product being used. The composition of the beef tea is indicated in table 50. (See page 124.) The method of preparation from the fresh beef was as follows:

The beef (from the top of the round) was freed so far as possible from all visible fat and connective tissue, then chopped and covered with cold water to extract the juices; finally both meat and liquid were heated slowly to about 80° C. For a few experiments it was heated only to 40° C. The liquid was carefully filtered to remove the solid material and then cooled. To prepare it for the experiment the solidified fat was removed, and the remainder reheated to approximately 80° C. Salt was added to taste by the subject.

It is obvious that beef tea, prepared from either the fresh meat or the extract, would contain considerable amounts of creatine and creatinine.2 In some instances the analyses showed a large proportion of nitrogen, particularly in the experiment of May 9, 1907, in which 6.82 grams of nitrogen were taken in 1,605 grams of beef tea. Thus the beef tea, particularly that made from the fresh beef, did not consist wholly of extractives, but in all probability it contained an appreciable amount of protein. Accordingly, we must also consider here the possibility of a true protein ingestion.

1Pettenkofer and Voit, Zeitschr. f. Biol., 1866, 2, p. 459.

The amount of creatine and creatinine in the beef tea used in the Middletown experiments was determined through the kindness of Dr. Victor C. Myers, at that time assistant pathologist at the Connecticut Hospital for the Insane and at present director of the Laboratory of Pathological Chemistry in the New York Post-Graduate Medical School and Hospital.

In a few of the calorimeter experiments the beef tea was given to the subject cold, but usually it was taken hot; the temperature of the liquid is recorded for each experiment in the statistical tables, also in the summary tables. In the respiration experiments, much smaller amounts were given than in the calorimeter experiments and the temperature was usually between 50° and 60° C. The total increment in the metabolism was computed for the respiration experiments by the planimeter method as described in the section on the ingestion of coffee. (See page 151.) Statistical data not included in the tables or in the discussion are given in the following paragraphs for all of the experiments. In this and subsequent statistics, the times given include both basal and food periods if the basal values were determined immediately before the ingestion of the food.