With Histological Report by G. Lyon, and a Report on the Nitrogen Excretion by Andrew Hunter.2

Attention is here directed to the influence of a meat diet on the structure of the kidneys.

The diets employed were five in number - rice boiled in water, oatmeal porridge made with skimmed milk and water, uncooked horse-flesh, uncooked ox-flesh, and a control diet of bread soaked in skimmed milk. The chemical composition and heat values of these foods were determined by Dr Andrew Hunter, and are given in a former section, along with the results on weight and growth of the animals. The present communication deals with the influence of a meat diet - horse-flesh and ox-flesh - on the kidneys. Four series of observations were made as follows: -

1 Frederick Gardiner, M.D., Journal of Physiology, vol. xxxiv. 2 Chalmers Watson, Internationalen Monatsschrift fur Anatomic und Physiologie, bd. xxiv., 1907.

I. On adult rats (seven) fed on a horse-flesh diet for five months. Thirteen controls were employed, seven being porridge-fed and six bread-and-milk-fed subjects.

II. On young animals (eight), the diet (horse-flesh or ox-flesh) being begun either when the animals were weaned, or at the age of two to three months.

III. On castrated female rats (five) aet. approximately six months, fed on a horse-flesh diet for four or five months. The controls were eight in number, five being rice-fed and three porridge-fed animals.

IV. On the second generation of meat-fed animals (horse-flesh and ox-flesh). This series comprises thirty-two animals of ages varying from twelve days to three months: it includes thirteen rats which had not been weaned.

The special points to which attention was directed were (a) the weight of the kidneys, and (b) their minute structure.

(A) The Weight Of The Kidneys

The weights are given in the form of tables. Each table records the number of animals on the meat and on the control diets, the total weight of the animals at death, their maximum weight during life, the total weight of the kidneys, and the percentage weight of the kidneys calculated from the weight of the animals at death. The duration of the special feeding and the mortality are also stated. As there are difficulties in the way of drawing deductions from the records of animals which had lost much weight during the observation, these are excluded, and attention is directed solely to the kidneys of animals which had not materially lost weight on the meat diet. In experiments I. and II., a certain loss of weight recorded in the case of the meat-fed subjects is balanced by a corresponding loss in the case of the controls.

Table I. Adult Rats

Table II. Castrated Female Raff

Table III. Young Rats

A. Meat Diet Commenced When The Animals Were Two To Three Months Old

B. Diet Commenced When The Animals Were Weaned, The Controls Being From The Same Litter

Table IV. Second Generation Of Meat-Fed Rats

A. One Litter Of Ox-Flesh-Fed Rats Aet

Three months, with an average weight of 68 grammes, the control series being rice-fed subjects whose growth had been arrested by the use of the rice diet, their average weight being 68 grammes.

1 In all cases under this table the young were put on meat diet at weaning. The age given denotes age at death.

B. One Litter Of Three Horse Flesh-Fed Rats Aet. Three Months, With One Control Of Exactly The Same Age

C. One Litter Of Five Ox-Flesh-Fed Subjects Aet

Two months; the controls in this series were either fed on a bread and whole milk, or on a mixed diet containing a large amount of rice (no meat diet).

D. A Series Of Five Horse-Flesh-Fed Rats From Three Litters, Their Ages Varying From Five To Eight Weeks

E. A Series Of Thirteen Rats From Three Meat-Fed Mothers), That Died Before They Were Weaned; With Eight Controls (One Litter)

A perusal of the above tables shows that the percentage weight of the kidneys is decidedly higher in meat-fed animals than in animals on a meat-free diet. A general summary of the results of the four series of observations is presented in Table V. Of fifty-two animals fed on a meat diet, the total weight was 4666 grammes, the total weight of the kidneys being 63.39 grammes, or 1.40 per cent; whereas of fifty-five rats on the meat free diets, with a total weight of6895 grammes, the total weight of Kidneys was 71.67, or 1.03 per cent.

Table V. General Summary Of Results

If we further compare the figures for the first and second generation of animals as given in Table VI., we find that the percentage weight of the kidneys in the second generation of meat-fed rats is decidedly higher than in the first generation - the figures being 1.59 grammes against 123 grammes per cent. So that the percentage weight of the kidneys in thirty-two animals of the second generation of meat-fed rats was more than 50 per cent, greater than that of twenty-eight controls.

Table VI. Comparison Of Weights In First And Second Generation Of Meat-Fed Animals

In four animals which were fed on an exclusive ox-flesh diet for nine months, the diet being commenced when the animals were about three months old, the result was different from those of the preceding observations All four animals in this series thrived on the diet, and gained in weight more than the controls. Their general appearance was that of good health, except that they were inordinately fat. One died suddenly after four and a half months of the diet, the remaining three were killed after nine and a half months of special feeding. The kidneys of all four were large, and varied in weight from 2.8 to 37 grammes: the average percentage weight being 1.06 grammes, which may be regarded as normal. It has to be noticed, therefore, that in this group the results of the examination of the kidneys are not in conformity with those yielded by the large majority of the experiments here recorded. But it is to be remembered that these animals had put on an unusual amount of fat.