50 INTRODUCTION. 



the vegetable varieties. Vegetable sugar taken as food is 

 changed so as to resemble animal sugar, before it is absorbed. 

 In considering, then, the proximate principles of the body, we 

 have only to do with the animal sugars. 



There are two varieties of sugar manufactured in the 

 economy. The first is constantly formed by the liver, and is 

 found in this organ and the blood which circulates between 

 it and the lungs. This variety is called Liver /Sugar and, as 

 it appears in the urine of diabetics, is sometimes known un- 

 der the name of diabetic sugar. The second variety is only 

 present in the organism during lactation. It exists in the 

 inilk, and is called Milk Sugar. We have also sugar resulting 

 from the transformation by digestion of cane sugar and starch, 

 which is called Glucose. This resembles the liver sugar very 

 closely, and is, indeed, identical with it in composition, but 

 differs from it in the fact that it ferments less easily. 



The presence of sugar in the economy seems to be a ne- 

 cessity of existence. It, or starch which is readily converted 

 into glucose, constitutes an important and necessary element 

 of food. In early life large quantities are taken in with the 

 milk. This, however, does not seem to be sufficient to supply 

 the wants of the system, and we have it continually manufac- 

 tured in the interior of the body ; but once formed, or intro- 

 duced from without, it undergoes some transformation innutri- 

 tion, and is never discharged in health. Sugar is exceedingly 

 soluble, and in the economy, exists in solution in the blood. 

 Here it forms a union with the chloride of sodium, which 

 masks, to a certain extent, some of its characteristic proper- 

 ties, such as the peculiar taste by which it is so readily 

 recognized. 



Composition and Properties. The sugars are composed 

 of carbon, hydrogen, and oxygen ; and it is noticeable that the 

 hydrogen and oxygen always exist in equal proportions, or 

 in the proportions which form water ; a peculiarity affording 

 an explanation of the transformation of one variety of sugar 



