58 THE PHYSIOLOGY OF PROTEIN METABOLISM 



Composition of the Tissues. 



Pfltiger and the majority of workers in this field held that the com- 

 position of the tissues did not appreciably alter by altering the nature 

 of the food. Rubner, on the other hand, maintained that the composi- 

 tion of the tissues could be altered if they be deprived of certain food 

 materials. Stockhausen (386) carried out elaborate analyses of the 

 tissues of two sets of dogs. An adult and a young growing dog were 

 fed on a protein (flesh) diet and an adult and young growing dog were 

 fed on a diet of rice. He found that the muscles of both the flesh-fed 

 dogs contained more nitrogenous material than the rice-fed ; those of 

 the adult dog fed on rice contained 88 per cent, of nitrogen, on flesh 

 94 per cent. ; those of the young dog fed on rice contained 93 per cent, 

 nitrogen, on flesh 94 per cent. A like condition was also noted in the 

 case of the liver. The liver of the adult dog fed on rice contained 65 

 per cent, of nitrogenous material and that on flesh 88 per cent. ; in the 

 case of the young growing dog when rice-fed the liver had 66 per cent, 

 and when flesh-fed 91 per cent, of nitrogenous material. Stockhausen 

 further made some interesting observations on the relation of nitrogen 

 to carbon in the tissues of his rice- and flesh-fed dogs. He found that 

 in the case of the rice-fed dogs, taking both together, the ratio of 

 nitrogen to carbon was as I : 3-30 and that in the flesh-fed dogs it was 

 as I : 3*28. Therefore in young growing dogs, when the tissue growth 

 and exchange was extremely active, very decided change in diet caused 

 but little or no alteration in the composition of the tissues. 



Miiller (292) carried out a very interesting experiment in this con- 

 nexion. He fed a dog for six weeks on a meat-free diet of rice, lard, 

 salts and water, and at the end of this period of feeding he amputated 

 a hind limb the muscles of which were used for an examination of the 

 composition of the tissues. After recovery from the operation he fed 

 the animal for another six weeks on large quantities of horse flesh, 

 and at the end of the period the animal was killed and again the ap- 

 propriate tissue was taken for examination. As a result of his analysis 

 Miiller came to the conclusion that a special nitrogenous store material 

 was formed which differed in its elementary composition from muscle 

 protein, as it was particularly rich in nitrogen. He believed that the 

 formation of this nitrogen-rich carbon-poor store substance accounted 

 for the large retention of nitrogen which had been observed from time 

 to time after a diet rich in protein. 



Zisterer (425) has also investigated this question. In the first place 



