the influence of the diet with different content of magnesium on certain chemical and physical properties of the bones the influence of the diet with different magnesium content on chosen chemical and physical properties of bones of young rats was investigated in the first part of the work the influence of the calcium level in the diet on the content of magnesium and some other mineral constituents in bone was also studied the investigations were carried out on growing wistar rats weighing 96100 g during 21 days the animals were fed the following semisynthetic diets a with different content of calcium 0214 0418 0610 0815 ca and the same level of magnesium av 554 ppm mg b with different content of magnesium and the same level of calcium av 0614 ca the content of phosphorus was the same 0440 in all the diets the control diet contained 0610 ca 044 p and 550 ppm mg after 21 days of experiment the animals were killed by anesthesia and the femurs and humeri were isolated they constituted the material for investigations the results of the investigations showed that the variable level of calcium from 0214 to 0815 in the diet with the same level of magnesium did not influence the content of magnesium and phosphorus in dry fatfree weight of bones the body weight of rats fed the diets with different content of calcium was very similar to the control group on the contrary the weight of femurs and calcium content in dry fatfree weight of bones of rats fed the diet with the lowest level of calcium 0214 were smaller than in the control group in the group of rats fed the diet with 60 ppm mg the visual symptoms of magnesium deficiency appeared after 7 days of the experiment after 21 days the body weight and length of bones in this group were smaller than in the control group also the content of magnesium and phosphorus in dry fatfree weight of bones breaking strength and the strength of twisting destroying moment of bones were lower in this group of rats as compared with the control one for most indices p less than 001 the group of rats fed the diet with 120 ppm mg differed from the control group only by smaller content of magnesium in dry fatfree weight of bones there was no statistically significant difference in the group of rats fed the diet with 2060 mg regarding all indices except for the phosphorus from the control group