8o 



Scientific Proceedings (28). 



of fine non-medullated nerve fibers intermingled with numerous 

 large ganglion cells. There are also large capsules filled with 

 nerve cells. Some of these oval-shaped capsules send out quite 

 large nerve tracts, others give off only fine nerve fibers. With 

 the intravital method of staining, fine nerve plexuses can be seen 

 all over surrounding muscle fibers. 



According to these studies the lizard heart may serve as a 

 typical instance of a purely neurogenic origin of the coordination 

 of the heart beats. 



43 (299) 



The influence of diet on the chemical composition of the body. 1 



By LAFAYETTE B. MENDEL. 



[From the Sheffield Laboratory of Physiological Chemistry, Yale 



University. ] 



The investigation was an attempt to ascertain to what extent, 

 if at all, the fundamental chemical structure of an organism can 

 be altered by variations in diet or changed nutritive conditions. 

 White mice were kept on dietaries of widely different character, 

 e - g-, high protein, protein and fat, low protein and carbohydrate, 

 etc., during considerable periods of time, and then killed and 

 analyzed. The data are being published elsewhere. They are 

 interpreted to indicate that although the fat and water content of 

 such organisms show variations through a veiy wide range, there 

 is a constant interdependence, even in cases of malnutrition. High 

 content of fat is accompanied by lower water content, and vice 

 versa. When the water content of the body is calculated on the 

 basis of the fat-free tissue, the range of variation is remarkably 

 small (70 to 74 per cent, of water). In order to afford some 

 direct basis for a comparison of the tissue substance aside from its 

 water and fat and the inorganic skeletal structure, the nitrogen 

 content of the entire animals was calculated on a water-, fat- and 

 ash-free basis. With few exceptions the animals afforded figures 

 within narrow range above or below 16 per cent, of nitrogen. 

 The constancy of composition of the organism suggests that it is 



1 This research was conducted with the aid of a grant from the Carnegie Institu- 

 tion of Washington. 



