APPENDIX. 



341 



gen, Nitrogen, Carburetted and Sulphuretted hydrogen, and Carbonic 

 acid. The first three have been referred to (p. 325, Vol. II.). Car- 

 buretted and sulphuretted hydrogen are found in the intestinal canal. 

 Carbonic acid is present in the blood and other fluids, and is excreted in 

 large quantities by the lungs, and in very minute amount by the skin. 

 It will be specially considered in the chapter on Respiration. 



Water, the most abundant of the proximate principles, 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 (quoted by Dalton, from Robin and Ver- 

 deiFs table, compiled from various authors) : 



QUANTITY OF WATER IK 1000 PARTS. 



Teeth 100 



Bones 130 



Cartilage 550 



Muscles 750 



Ligament . 768 



Brain 789 



Blood 795 



Synovia 805 



Bile 880 



Milk 887 



Pancreatic juice 900 



Urine 936 



Lymph 960 



Gastric juice 975 



Perspiration 986 



Saliva 995 



Uses of the Water of the Body. The importance of water as a 

 constituent of the animal body may be assumed from the preceding table, 

 and is shown in a still more striking manner by its withdrawal. If any 

 tissue as muscle, cartilage, or tendon be subjected to heat sufficient to 

 drive off the greater part of its water, all its characteristic physical prop- 

 erties are destroyed; and what was previously soft, elastic, and flexible, 

 becomes hard and brittle, and horny, so as to be scarcely recognizable. 



In all the fluids of the body blood, lymph, etc., water acts the part 

 of a general solvent, and by its means alone circulation 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. 



Source. 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 blood and tissues. The total amount taken into the body 

 every day is about 4J- Ibs. ; while an uncertain quantity (perhaps J- to 

 f Ib.) is formed by chemical action within it. (Dalton.) 



Loss. The loss of water from the body is intimately connected with 

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



