INORGANIC CELL-CONSTITUENTS. 129 



food undergoes chemical decomposition in the bod}', as will be alluded 

 to in the subject of Nutrition. Thus, the potassium chloride of muscles 

 and red blood-corpuscles apparent!}^ originates in a double decomposition 

 of sodium chloride and potassium phosphate into sodium phosphate and 

 potassium chloride. Possibly the hydrochloric acid of the gastric juice 

 and the sodium salts of the bile have similar origins. 



Sodium chloride is absolutely essential to the manifestation of life ; 

 in a physical sense, it is of great importance, from the influence which it 

 exerts over diffusion, particularly in the degree of absorption from the 

 alimentary canal. The conditions which follow the deprivation of 

 sodium chloride, and a more detailed account of its relations to the 

 nutritive processes and body will again be referred to more at length 

 under the subject of Nutrition. 



3. POTASSIUM CHLORIDE (KC1). Potassium chloride is usually a 

 companion of sodium chloride, although in certain tissues, such as the 

 red blood-corpuscles, and in muscles, it occurs in greater amount than 

 the sodium salt, while it is almost absent from the blood-plasma, where 

 a slight excess of potassium salts appears to act as a poison to the heart. 

 A similar toxic effect is also exerted by potassium chloride on muscles 

 and nerves. 



In the herbivora potassium chloride is, as a rule, in excess over 

 sodium chloride. The salivary glands and kidneys appear to be the 

 special organs for its elimination. 



4. SODIUM AND POTASSIUM CARBONATES (C0 8 Na a , CO,XaH, 3(CO,)- 

 Na 4 H 2 , CO 8 K a , CO 8 KH). These salts are found in the ash of various 

 organic substances, w r here they have probably originated from the 

 decomposition of various organic acid compounds of sodium and potas- 

 sium. In various animal juices, however, and especially in the blood 

 and urine of herbivorous 'animals, and in the blood of the omnivora, 

 sodium and potassium carbonates exist already formed. When car- 

 nivorous animals are fed on a vegetable diet their urine contains 

 considerable quantities of carbonates of the alkalies, resembling thus the 

 urine of herbivorous animals in reaction and constitution ; it will be 

 alkaline in reaction, turbid, and deposit a calcareous sediment, instead of 

 being acid and clear, as is normally the case in the urine of carnivora. 

 It is also interesting, in this connection, to notice that the urine of the 

 suckling calf before being weaned is clear and acid, as among carnivora; 

 when the calf is placed on a vegetable diet the urine becomes turbid 

 and alkaline. Further, if herbivorous animals are allowed to fast, their 

 urine becomes acid and clear, for they are then living at the expense 

 of their own tissues, and are practically carnivorous. Sodium carbonate 

 is also found in the lymph and the parotid saliva of the horse. 



These salts, when found as constituents of animal cells and fluids, 



