UNDERGOES COMBUSTION. 61 



the metamorphosed tissues ; this carbon disappears 

 in the animal body, and the bile likewise disappears 

 in the vital process. Its carbon and hydrogen are 

 given out through the skin and lungs as carbonic 

 acid and water; and hence it is obvious that the 

 elements of the bile serve for respiration and 

 for the production of animal heat. Every part of 

 the food of carnivorous animals is capable of 

 forming blood ; their excrements, excluding the 

 urine, contain only inorganic substances, such as 

 phosphate of lime ; and the small quantity of organic 

 matter which is found mixed with these is derived 

 from excretions, the use of which is to promote 

 their passage through the intestines, such as mucus. 

 These excrements contain no bile and no soda ; for 

 water extracts from them no trace of any substance 

 resembling bile, and yet bile is very soluble in 

 water, and mixes with it in every proportion. 



Physiologists can entertain no doubt as to the 

 origin of the constituent parts of the urine and of 

 the bile. When, from deprivation of food, the 

 stomach contracts itself so as to resemble a portion 

 of intestine, the gall-bladder, for want of the motion 

 which the full stomach gives to it, cannot pour out 

 the bile it contains ; hence in animals starved to 

 death we find the gall-bladder distended and full. 

 The secretion of bile and of urine goes on during 

 the winter sleep of hybernating animals ; and we 

 know that the urine of dogs, fed for three weeks 

 exclusively on pure sugar, contains as much of the 



