44 INTRODUCTION. 



lates, citrates, and acetates of lime contained in the food. 

 These salts, meeting with carbonic acid, are decomposed, and 

 the carbonate of lime is formed. It is probable that in the 

 human subject some of it is changed into the phosphate of 

 lime, and in this form is discharged in the urine ; but when 

 and how this change takes place has not been definitely as- 

 certained. 



Carbonate of Soda, NaO, CO 2 + 10 HO. 



Carbonate of soda is found in the blood and saliva, giv- 

 ing to these fluids their alkalinity ; in the urine of the hu- 

 man subject, when it is alkaline without being ammoniacal ; 

 in the urine of the herbivora ; in the lymph, cephalo-rachid- 

 ian fluid, and bone. The analyses of chemists with regard 

 to this substance are very, contradictory, on account of its 

 formation during the process of incineration ; but there is no 

 doubt that it is found in the above situations. The follow- 

 ing table gives the quantities which have been found in some 

 of the fluids and solids : 



Table of Quantity of Carbonate of Soda. 



Parts per 1,000. 



In Blood of the Ox (Marcet) 1-62 



" Lymph (Nasse) 0'56 



" Cephalo-rachidian Fluid (Lassaigne) 0'60 



" Compact Tissue of Tibia in Male of 38 years (Valentin) 2-00 

 " Spongy Tissue of the same (Valentin). . 0*70 



Function of Carbonate of Soda. This substance has a 

 tendency to maintain the fluidity of the fibrin and albumen of 

 the blood, and assists in preserving the form and consistence 

 of the blood corpuscles. Its function with regard to nutri- 

 tion is rather accessory, like that of chloride of sodium, than 

 essential, like the phosphate of lime in the constitution of 

 certain structures. 



