I9I2] Lafayette B. Mendel 137 



changes due to osmosis. Liebig's extract of beef is without influ- 

 ence on the metabolism. Fifty grams of olive oil cause a consider- 

 able increase in heat production. GlycocoU causes a very great in- 

 crease in heat production, alanin also acts powerfully, leucin and ty- 

 rosin less so and glutamic acid not at all. 



It is concluded that the heat production may be increased by 

 increasing the quantity of sugar and fat reaching the cells, or it may 

 be increased through the direct Stimulation of the cells by amino- 

 acids, notably glycocoll and alanin. 



Nutrition and bone growth 



FRANCIS H. MCCRUDDEN 



The question of the nature of bone metabolism in health and 

 disease is one that until recently can hardly be said to have been 

 attacked experimentally. The pathologists, with one or two excep- 

 tions, have generally considered bone as a dead tissue not undergo- 

 ing metabolism, once it is laid down. This opinion has, of course, 

 colored their views regarding the nature of the process in various 

 bone diseases. In osteomalacia, for example, a disease in which 

 there is a decrease in the mineral content of the bone, it has been 

 supposed that the process is due to the action of an acid which dis- 

 solves out the mineral constituents. 



Numerous investigations, chemical, histological and clinical, dur- 

 ing the last few years have shown that these views regarding the 

 nature of the process in osteomalacia and the nature of normal bone 

 metabolism cannot be correct. Bone, like the other tissues, under- 

 goes metabolism throughout life. Old bone is continuously being 

 resorbed and new bone laid down. If the new bone laid down is 

 not qualitatively of the right composition, the result may be rickets, 

 osteomalacia, osteoporosis, or Osteitis deformans, depending on the 

 age of the patient and other factors. The bones act as a störe of 

 lime salts to be called on in time of need just as the subcutaneous 

 tissue acts as a störe of fat and the liver as a störe of glycogen; and 

 a flux of calcium from the bones started by a growing fetus, a 

 hardening callus, metastatic bone formation, etc., may, under cer- 

 tain circumstances, lead to decalcification enough to result in osteo- 



