LABORATORY EXPERIMENTS 95 



cles, and many tissues, and in lymph and chyle, albumin of serum, fibrin, 

 bile, milk, and other fluids. A salt of iron, probably a phosphate, exists in 

 the hair, black pigment, and other deeply colored epithelial or horny substances. 

 Water. Water forms a large proportion, more than two-thirds, 

 of the weight of the whole body. Its relative amount in some of the principal 

 solids and fluids of the body is shown in the following table (from Robin 

 and Verdeil): 



Quantity of Water in Per Cent. 



Teeth 10.0 Bile 88.0 



Bones 13.0 Milk 88.7 



Cartilage 55 - Pancreatic juice 9- 



Muscles 75- Urine 93-6 



Ligament 76.8 Lymph 96.0 



Brain 7&-9 Gastric juice 97-5 



Blood 79 . 5 Perspiration 98 . 6 



Synovia 80.5 Saliva 99-5 



In all the fluids and tissues of the body blood, lymph, muscle, gland, 

 etc. water acts the part of a general solvent, and by its means alone circula- 

 tion of nutrient matter is possible. It is the medium also in which all fluid 

 and solid aliments are dissolved before absorption, as well as the means by 

 which all, except gaseous, excretory products are removed. All the various 

 processes of secretion, transudation, and nutrition depend of necessity on 

 its presence for their performance. 



The greater part, by far, of the water present in the body is taken into 

 it as such from without, in the food and drink. A small amount, however, 

 is the result of the chemical union of hydrogen with oxygen in the oxida- 

 tions of the body. 



The loss of water from the body is intimately connected with excretion 

 from the lungs, skin, and kidneys, and, to a less extent, from the alimentary 

 canal. The loss from these various organs may be thus apportioned (quoted 

 by Dalton from various observers): 



From the Alimentary canal (feces) 4 per cent 



" Lungs 20 " 



" Skin (perspiration) 30 " 



" Kidneys (urine) 46 " 



LABORATORY EXPERIMENTS ON THE CHEMISTRY OF THE 



BODY. 



Proteid General Reactions. Certain tests depending on the pres- 

 ence of one or more of the constituent groups in the proteid molecule, 

 while not conclusive each in itself, when taken together serve for proteid 



