COAGULATION. 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. 2 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, 6 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 0*276, 

 the estimation by titration of the same blood after laking gave a result 

 as high as - 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 

 (hydrodisodic phosphate and sodic bicarbonate) which are theoretically 

 acid, 8 having the power both of fixing bases and of turning other acids 

 out of combination (Kollett). 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 grms. blood ; being increased in conditions of fever to 0-272 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. 



3 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. Iviii. S. 507. 



4 Minkowski, Arch. f. exper. Path. u. Pharmakol., Leipzig, Bd. xix. S. 209; Mitth. 

 a. d. med. Klin. z. Konigsberg, Leipzig, 1888, S. 174. 



5 C. Schmidt, "Charakt. d. epid. Cholera," Leipzig, 1850 ; Straus, Roux, Thuiller et 

 Nocard, Compt. rend. Hoc. d. biol., Paris, 1883, S. 569. 



6 Arch.f. Physiol., Leipzig, 1893, S. 556. 



7 Zuntz in Hermann's "Handbuch," 1880, Bd. iv. Th. 2, S. 77. 



8 Maly, Sitzungsb. d. k. Akad. d. Wissensch., Wieu, 1878, Bd. Ixxvi. Abth. 2, S. 21 ; 

 and ibid., 1882, Bd. Ixxxv. Abth. 3, S. 314. 



9 Op. cit. 



10 Hevvson, "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, et path., 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, Journ. Physiol., Cambridge and London, 

 1897, vol. xxi. p. 403. 

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