7 7 2 CHEMISTR Y OF RESPIRA TION. 



was avoided in the analyses made by Zimtz, by the addition of distilled water 

 in sufficient quantity to maintain the concentration of the fluid at its original 

 point. Preyer l found that the proportion of carbon dioxide in loose and in 

 firm combination was as 2 to 3 '5. 



The next question to discuss is the nature of the substances with 

 which the carbon dioxide is combined. The facts already mentioned 

 show that these substances are to be sought chiefly in the serum. In 

 the first place, analyses of the ash of serum show that the most important 

 constituents are the alkalies ; thus, according to Bunge's 2 experiments, 

 the ash from 1000 gnus, of dog's serum contains 4*341 grms. sodium, of 

 which 3403 grms. is sufficient to saturate the chlorine. The remainder, 

 0'878 grms. sodium, can combine with 0'623 grms. carbon dioxide (316 

 c.c. at and 760 mm.) to form sodium carbonate, and, in addition, with 

 another equal quantity to form sodium bicarbonate. Thus calculated, 

 a litre of plasma could hold 632 c.c. of carbon dioxide, or 63 volumes 

 per cent, in chemical combination. This must be considered only as an 

 approximate result, for the amount of sodium carbonate in serum cannot 

 be accurately determined by an analysis of the ash or by titration, for 

 the alkali is combined with other substances, especially with proteids. 3 



The alkalies of the blood are the most important constituents for 

 holding carbon dioxide in combination. Serum freed from gas can 

 combine with as much carbon dioxide as is necessary to form bicarbonates 

 with its alkalies ; any reduction in the alkalinity of the blood is accom- 

 panied by a decrease in carbon dioxide. Thus Walter 4 found only 

 2 to 3 volumes per cent, of carbon dioxide in the blood of rabbits poisoned 

 by hydrochloric acid ; Geppert and Zuntz 5 observed that the alkalinity 

 of the blood of rabbits was diminished by -the acid formed during tetanic 

 muscular activity, and at the same time there was a decrease in the 

 carbon dioxide of the blood. During diabetic coma the alkali of the blood 

 appears to be in great part neutralised by combination with /3-oxybutyric 

 acid ; 6 and Minkowski 7 found only 3*3 volumes per cent, of carbon 

 dioxide in the blood of a patient suffering from diabetic coma. 



Another substance with which the carbon dioxide is supposed to 

 combine in serum is disodium hydrogen phosphate 8 (Na 2 HP0 4 ), with the 

 formation of sodium bicarbonate and sodium biphosphate. Thus 



Na 2 HP0 4 + C0 2 + H 2 = NaHC0 3 + NaH 2 P0 4 . 



Sertoli 9 and Mroczkowski, 10 however, found that the quantity of 

 phosphoric acid in the serum is so small that, if allowance be made for 

 that contained in lecithin and nuclein, the amount is quite insufficient 



1 Sitzungsb. d. k. AJcad. d. Wissensch. Math.-naturw. CL, Wien, Bd. xlix. S. 27. 



2 Ztschr. f. Biol., Miinchen, 1876, Bd. xii. S. 204; "Lehrbuch der physiologischen 

 und pathologisclien Chemie," Leipzig, 1889, S. 254. 



3 Hoppe-Seyler, "Physiol. Chem.," Berlin, 1879, Bd. iii. S. 502; Sertoli, Med.- 

 chem. Untersuch., Berlin, 1868, Heft 3, S. 350. 



4 Arch.f. exper. Path. u. Pharmakol., Leipzig, Bd. vii. 



5 Arch.f. d. ges. Physiol., Bonn, 1888, Bd. xlii. S. 189. See also this article, p. 714. 



6 Stadelmann, Arch. f. exper. Path. u. PharmakoL, Leipzig, Bd. vii. ; Minkowski, 

 ibid., Bd. xviii. ; Mitth. a. d. med. Klin, zu Konigsberg, Leipzig, 1888. 



7 Loc. cit. 



8 Fernet, Ann. d. sc. not., Paris, Ser. 4, tome viii. p. 160 ; Heidenhain and L. Meyer, 

 Stud. d. physiol. Inst. zu Breslau, Leipzig, 1863, Het't 2 ; Ann. d. Chem. u. Pharm., 

 1862-63, Supp. Bd. ii. S. 157. 



9 Hoppe-Seyler, Med.-chem. Untersuch., Berlin, 1868, Heft 3, S. 350. 

 10 Centralbl.f. d. med. Wissensch., Berlin, 1878, No. 20, S. 356. 



