BODY TISSUES AND FLUIDS 445 



only slight glycosuria, showing that the threshold point has been raised, 

 apparently due in many instances to an accompanying nephritis. The 

 cause of glycosuria in "renal diabetes" is obviously due to the reverse condi- 

 tion, viz., a threshold point helow the level of the normal blood sugar. 



A simple method of estimating the diastatic activity of the blood has 

 been described by Myers and Killian (a) who have called attention to the 

 fact that conditions of hyperglycemia are associated with an increased dias- 

 tatic activity and have suggested that this might be the important factor in 

 the production of the hyperglycemia in both diabetes and nephritis. The 

 increase in the diastase of the blood in nephritis finds probable explanation 

 in the decreased excretion of diastase in the urine, now well known in this 

 condition, although a satisfactory explanation of the increased activity in 

 diabetes is not so readily given. So-called alimentary glycosuria is ap- 

 parently due to an increased activity on the part of this diastatic ferment, 

 thus impairing the body's power to store glycogen. Hyperf unction on the 

 part of the ductless glands, hyperthyroidism for example/ appears to 

 result in an increase in the blood diastase, while hypof unction seems to 

 have the reverse effect. 



Blood Lipoids 



Material contributions to our knowledge of the blood lipoids and fat 

 metabolism have been made during the past ten years. The blood lipoids 

 comprise (1) the true fats glycerids of the fatty acids; (2) the phos- 

 phatids lecithin, cephalin, etc., ordinarily called lecithin, and (3) choles- 

 terol with its fatty acid esters. Although these substances were originally 

 grouped together on account of similar solvent properties, it would now 

 appear that they are closely connected in metabolism. 



Bloor (d) has carried out experiments which support the older concep- 

 tion of fat digestion, i. e., the food fat is saponified in the intestine, al> 

 sorbed in water soluble form as soaps and glycerol, resynthesized by the in- 

 testinal cells, and passed into the chyle and thence to the blood as neutral fat 

 suspended in the plasma in a very fine condition. About 60 per cent of the 

 food fat has actually been accounted for in the chyle in this way and this 

 figure is probably low. The remaining smaller quantity is generally as- 

 sumed to be absorbed directly into the blood stream by way of the in- 

 testinal capillaries. 



In a study of the blood lipoids during fat assimilation, Bloor (e) has ob- 

 served that (1) the total fatty acids increase in both plasma and corpuscles 

 but the increase is generally more marked in the corpuscles; (2) lecithin 

 increases greatly in the corpuscles, but only slightly in the plasma ; (3) no 

 definite change takes place in the quantity of cholesterol and (4) a fairly 

 constant relationship exists between the total fatty acids and lecithin of 



