THE BLOOD. 23! 



present and apparently, also, pentoses in traces. As glucose 

 and fructose yield the same osozone this simple reaction can- 

 not be applied to detect a fructose content. Occasionally small 

 amounts of disaccharides appear to be present. Of these mal- 

 tose passes into dextrose by inversion, while saccharose and 

 lactose would be eliminated as such by the kidney. Gluco- 

 ronic acid in combination is also present and this may be con- 

 founded with a sugar in some of the tests. More will be 

 found on this point in a following chapter. 



SALTS OF THE BLOOD. 



The total mineral matters of the blood, exclusive of the iron 

 of the hemoglobin, amount to a fraction of one per cent only, 

 but still are of very considerable importance. These salts are 

 largely the chlorides, phosphates and carbonates of the alkali 

 metals, the potassium salts being most abundant in the cor- 

 puscles, while the sodium salts are most characteristic of the 

 plasma. It is believed that the variations in this salt content 

 are very small normally. The nearly constant osmotic pres- 

 sure of the blood points to this. Slight changes are speedily 

 corrected by the kidneys. 



Ex. The presence of reducing carbohydrate and salts in the blood may 

 be demonstrated in this way. Mix about 50 cc. of fresh blood with 300 

 cc. of water and boil vigorously a few minutes. A drop or two of acetic 

 acid may be added during the boiling to maintain a nearly neutral reac- 

 tion. Filter and divide the nitrate, which should be perfectly clear, into 

 two parts. Concentrate one-half to a volume of about 10 cc. and apply 

 the Fehling test for sugar. Concentrate the other half likewise and use 

 portions for tests for phosphates and chlorides. The sulphate test usually 

 fails with the volume of blood taken. Evaporate a small portion of this 

 concentrate nearly to dryness on a glass slide, allow what is left to cool 

 and crystallize. Sodium chloride crystals may be recognized by the micro- 

 scope. To some of the evaporated residue apply the flame test (with 

 spectroscope) for potassium. 



GASES OF THE BLOOD. 



The blood holds several gases in loose combination. These 

 are principally oxygen, nitrogen and carbon dioxide. Minute 

 traces of argon seem to be present also, which like the more 



