88 
Proceedings of Royal Society of Edinburgh. [sess. 
The observations have been as follows : — 
(a) On very young rats newly weaned, the controls being taken 
from the same litter (10 litters). 
(b) On young rats set. 2 to 3 months (14 on each diet). 
( c ) On adult rats (10 on each diet). 
(d) On castrated female rats * (17). 
Throughout the observations the bread and skim-milk diet was 
employed as the control diet ; it appears to be well adapted for 
the growth and nutrition of rats of all ages (see Charts I., II., 
III., IV.). 
Special attention was directed to the influence of the various 
diets on the supervention of pregnancy, on the growth and nutri- 
tion of the animals in the second generation, and on the recuperative 
power of animals under a normal diet that had deteriorated in 
consequence of having been fed for a time, in some cases for more 
than one generation, on an unphysiological diet. 
Results. 
Rice. — An exclusive diet of boiled rice arrests the growth of 
young rats. The animals always succumb eventually, although 
they may live for a few months. Adults lose weight rapidly, and 
die, as a rule, within two months. Castrated female rats tolerate 
the diet well, four out of five being alive and apparently in good 
health at the end of five months. 
Porridge. — This diet retards the growth and is speedily fatal 
to very young rats (see Chart I.) ; a similar result is observed in 
the case of young rats set. 2 to 3 months. Adult rats maintain 
their weight well for many months on this diet. It may be noted 
that the composition and heat value of the porridge is essentially 
the same as that of the bread and skim milk (see Table, p. 87). 
Horse Flesh. — In very young rats (newly weaned) a diet of 
horse flesh retards growth and is uniformly fatal within a few 
months (see Chart I.). Young rats set. 2 to 3 months exhibit a 
mixed result, the majority succumbing within a few months ; a 
minority live, thrive, and become pregnant. The power of lacta- 
* I am indebted to Dr F. H. A. Marshall and Mr W. A. Jolly for these 
animals. 
