CO A G ULA TION. 145 
acids by the mouth), whereas herbivora show no such resistance. 1 The 
result appears to be due to the fact that ammonia becomes split off from 
the superabundant proteid in place of urea, and serves to unite with 
and neutralise the excess of acid. 
Kraus found the alkalinity to be diminished by laking the blood, i.e. the 
blood to become more acid after the corpuscles are broken up, but Loewy and 
others have found it to be very high under these conditions ; alkaline substances 
in the corpuscles coming also into estimation.- It is diminished after with- 
drawal, and during the process of coagulation (Zuntz) ; 3 when this is completed, 
it is about *04 grm. NaHO less. The alkalinity is also diminished in fever and 
in many diseases. In diabetic coma 4 and in the cold stage of cholera 5 an 
acid reaction has even been detected. The diminution of alkalinity is accom- 
panied by a diminished amount of carbonic acid in the blood. 
The alkalinity is usually stated to be due to carbonate and phosphate 
of soda. This may be true for the alkalinity of the plasma, but it is 
insufficient to account for that of the corpuscles as well, and in them is 
probably largely due to the presence of organic substances of weak basic 
nature. Thus it was found by Zuntz and Lehmann, that whereas a 
sample of calcined blood showed an alkalinity equivalent to 0-240, and 
the estimation of the alkalinity of the same blood by the amount of 
carbonic acid it would combine with gave an alkalinity equal to - 276, 
the estimation by titration of the same blood after laking gave a result 
as high as 0-832. Saturation of blood with carbonic acid causes the 
corpuscles to become less and the serum more alkaline. 7 
Although the blood is alkaline in reaction to litmus, it contains salts 
(hydroclisodic phosphate and sodic bicarbonate) which are theoretically 
acid, 8 having the power both of fixing bases and of turning other acids 
out of combination (Eollett). In this sense the " acidity " as well as the 
" alkalinity " of the blood can be spoken of. According to Kraus 9 it is 
normally equivalent in venous blood to from 0-162 to 0-232 grm. NaHO per 
100 grins, blood ; being increased in conditions of fever to - 272 grm., and 
in diabetic coma to 0*347 grm. 
Coagulation. — -The blood begins to coagulate three or four 
minutes after it is drawn, and the process is completed in seven 
or eight minutes. 10 The process is hastened by warmth, by agita- 
1 Walter, Arch. f. exper. Path. u. Pharmakol., Leipzig, 1877, Bd. vii. S. 148. 
- Kraus, Ztschr. f. Heilk., 1890, Bd. x. S. 106 ; Arch. f. exper. Path. u. Pharmakol., 
Leipzig, 1889, Bd. xxvi. S. 186 ; Winternitz, Ztschr. f. physiol. Chem,, Strassburg, 1891, 
Bd. xv. S. 505 ; Loewy, Arch. f. d. ges. Physiol, Bonn, 1894, Bd. viii. S. 462 ; also Loewy 
and Zuntz, ibid., S. 511, and Lehmann, ibid., S. 428. See note on p. 144. 
3 See also Loewy and Zuntz, Arch. f. d. ges. Physiol., Bonn, 1894, Bd. lviii. S. 507. 
4 Minkowski, Arch. f. exper. Path. u. Pharmakol., Leipzig, Bd. xix. S. 209; Mitth. 
a. d. vied. Klin. z. Konigsberg, Leipzig, 1888, S. 174. 
5 C. Schmidt, "Charakt. d. epid. Cholera," Leipzig, 1850 ; Straus, Roux, Thuiller et 
Xocard, Compt. rend. Soc. d. biol., Paris, 1883, S. 569. 
6 Arch./. Physiol., Leipzig, 1893, S. 556. 
7 Zuntz in Hermann's "Handbuc.h," 1880, Bd. iv. Th. 2, S. 77. 
8 Maly, Sitziuigsb. d. k. ATcad. d. Wissensch., Wieu, 1878, Bd. lxxvi. Abth. 2, S. 21 ; 
and ibid,, 1882, Bd. Ixxxv. Abth. 3, S. 314. 
9 Op. cit. 
10 Hewson, "Properties of the Blood," 1772. In "Works," edited by G. Gulliver for 
the Sydenham Society, p. 24. Blood from the hepatic veins coagulates rather more 
slowly than blood from other parts of the vascular system. Paulesco {Arch. d. physiol. 
norm, etpath., Paris, 1897, p. 21) states that blood from the portal vein from animals in full 
digestion of proteid food may take as long as fifty minutes to coagulate, but otherwise there 
is little difference in blood from different vessels. For a method of accurately estimating 
the time of commencing coagulation, see Brodie, Jour it. Physiol., Cambridge and London, 
1897, vol. xxi. p. 403. 
VOL. I. — io 
