CARBONATE OF SODA. 439 



Nasse* found 0*056^ of carbonate of soda in the lymph of a 

 horse, while Marcetf found 0*1 65 in the serum of the blood. 

 Those who regard the kidneys as mere percolators cannot deny the 

 presence of alkaline carbonates in the blood, since the urine (at 

 least of herbivorous animals) contains a considerable amount of 

 carbonates. The parotid saliva of the horse becomes turbid, in 

 the same manner as lime-water, on exposure to the air, with, how- 

 ever, this difference, that it almost immediately deposites the most 

 beautiful microscopic crystals of carbonate of lime. 



Liebig was formerly of opinion that the carbonate of soda in the 

 blood acted an extremely important part in the process of respiration, 

 in short, that it was the means by which the carbonic acid is con- 

 veyed from the capillaries into the lungs. The oxygen mixed with 

 the blood in the lungs there displaces the carbonic acid as completely 

 as it would be expelled by a current of oxygen or hydrogen from 

 its state of combination in bicarbonate of soda. As far as our present 

 knowledge extends, no facts are at variance with this view; indeed, 

 if the presence of carbonate of soda in the blood be once granted, 

 no one can wonder that it is converted to the bicarbonate, and on 

 the other hand, that it must be decomposed on coming in contact 

 with other gases than carbonic acid. But the question naturally 

 suggests itself Is the quantity of carbonate of soda sufficient 

 to serve as a means of transport for the whole of the carbonic 

 acid of the blood ? The following calculation supplies the answer : 

 1000 grammes of blood contain 1*628 grammes of carbonate of 

 soda, which, to become converted into bicarbonate must take up 

 0'637 of a gramme of carbonic acid; hence 0'637 of a gramme of 

 carbonic acid can be extracted from the blood by the air-pump, or 

 expelled by other gases ; this would amount to 322 cc. according 

 to volume ; if we assume that the specific gravity of the blood is 

 1-055, then 1000 cc. of blood would contain 343 cc. of carbonic 

 acid, capable of being removed by other gases or by the air-pump. 

 Magnus has, however, succeeded in removing about 300 cc. of 

 carbonic acid from 1000 cc. of blood by means of hydrogen and a 

 vacuum ; a method by which a part of the carbonic acid must 

 always remain in the blood. The coincidence between the empi- 

 rical result and the calculation is quite as great as could be expected. 

 It cannot be doubted that the carbonate of soda in the blood 

 serves as a solvent for the fibrin as well as the albumen ; Bird, 

 has, however, shown that the bicarbonate is one of the best 



* Simon's Beitrage z. phys. u. pathol. Chem. Bd, 1, 8. 449. 

 t Medico. Chir. Trans, vol. 2, p. 370. 



