J2 FEEDING EXPERIMENTS WITH ISOLATED FOOD-SUBSTANCES. 



the particular dietaries adopted is derived from measurements on 

 three young rats of the same litter maintained for 124 days without 

 noteworthy growth, on a diet of 



Per cent. 



Glutenin 18.0 



Starch 14.5 to 34.5 



Sugar 15.0 to 20.0 



Agar 50 



Salt mixture 1 2.5 



Lard 20 . o to 45 . o 



The curves of growth of these animals as well as three others 

 from the same brood fed on mixed food or the milk-food mixture 

 (and showing a normal growth) are reproduced in Charts LXXXI, 

 LXXXII, LXXXIII, LXXXIV, LXXXV, and LXXXVI. 



The animals were killed at the age of 178 days and measurements 

 were made by Dr. S. Hatai, of the Wistar Institute. The tabulated 

 data are given on the following page, together with a report from Dr. 

 Hatai, to whom, as well as to Dr. Donaldson, we are greatly indebted 

 for helpful cooperation. 



The statistics of body-length, weight of brain, spinal cord, etc., 

 of the stunted animals at an age of 178 days are comparable with 

 those characteristic for normally growing rats of the same body- 

 weight, which is attained at an age of approximately 54 to 63 days. 

 Here, then, are illustrations of maintenance without growth. 



Dr. Hatai further reports as follows: 



vSince it seems to be'the least variable character, I have selected the body- 

 length as the basis for computation. When the other characters which we 

 can measure are calculated from the formulas based on body-length, it is 

 seen that the observed weight of the brain and of the spinal cord agrees 

 closely with the calculated in both the control and the stunted rats. Thus 

 both series have a growth of the nervous system normal to their body- 

 length. In the control series, the percentage of water observed in both the 

 brain and the spinal cord agrees with that calculated according to the body- 

 length. In general then the control rats agree with the general population 

 in these characters. Since the stunted rats have an abnormally small body- 

 length for their age, they can not be treated by the formula for determining 

 the percentage of water from body-length. When, however, we take the 

 estimated percentage of water for 178 days (see Donaldson*) we find that 

 this value agrees with that observed in the stunted series. It may be 

 further noted that the ratio between body-length and tail-length is the same 

 in both series. We therefore conclude that in both scries the body-weight is 

 normal to the body-length; the brain and spinal cord weight normal to the body- 

 length; and the percentage of water normal for age. Concerning other organs 

 we have no data, but we may infer from the foregoing that they also have 

 weights normal to the body-length. You will see from the above that the 

 stunted rats though small have the general relative development of the 

 Controls and that in the only case where it is possible to follow the maturing 

 process, that is in the percentage of water in the nervous system, they have 

 matured in accordance with their age (see Donaldson*). 



*Donaldson: Journal of Comparative Neurology, April 191 1. 



