36 SPECIFICITY OF THE BLOOD OF VERTEBRATES 



is far less variable quantitatively than hemoglobin, but there is no definite 

 relationship between the increase or decrease of one and the changes in 

 the other. 



THE ALKALINITY OF THE BLOOD IN RELATION TO GENERA. 



The reaction of the blood from the standpoint of modern physico- 

 chemistry is neutral, inasmuch as the blood does not contain a larger quan- 

 tity of hydroxyl ions (OH) than water. Moreover, this neutral state is 

 maintained with remarkable persistency, as is shown by the fact that a 

 very much larger quantity of sodium hydroxide is required to cause a 

 given intensity of reaction than when added to water. This peculiarity 

 is owing, according to Friedenthal, to the acid character of the proteins. 

 When, however, the blood is tested with litmus, lacmus or lacmoid, or by 

 titration with a weak acid, such as tartaric or phosphoric acid, a marked 

 degree of alkalinity will be found. In the case of the human blood, for 

 instance, it will be noted that 100 c.c. have an alkaline equivalent of from 

 250 to 300 mg. of NaOH, or in other words an alkalinity corresponding to 

 a 0.25 to 0.3 per cent aqueous solution of sodium hydroxide. The alkales- 

 cence thus expressed is the measure of the amount of bases in combina- 

 tion with weak acids in the form of weak basic bodies, such as certain of 

 the proteins, disodium phosphate, and sodium carbonate. 



That the degree of alkalinity must of necessity be variable, within 

 certain limits at least, seems apparent in the fact of the unceasing chemical 

 changes that take place within the blood, and in the continual passage of 

 substances of varying reactions between the blood and the tissues. It has 

 been shown that the intensity of the reaction may be affected to even a 

 marked degree by the character of the diet, by muscular exercise, and by 

 various other conditions, normal and abnormal; it decreases rapidly in the 

 shed blood and during the process of coagulation, and the more markedly 

 as the alkalinity was previously high; it is higher in the plasma than in 

 the serum and highest in the coagulum, and it is very high in laked blood; 

 and it varies within limits so wide in different species that the equivalent 

 of one may be as much as or more than twice as high as in another species. 



The alkalescence of human blood has been studied by a large number 

 of investigators, chiefly clinicians, and the values are far from being in 

 accord, the reason for which is not far to seek when one considers the crudi- 

 ties of some of the methods and the fact that the reaction alters within a 

 period so short as a couple of minutes after the blood is shed. According 

 to Strauss (Zeit. f. klin. Mi-dicin, 1896, xxx, 327) the unavoidable errors 

 may range as high as 30 mg. of NaOH per 100 c.c. of blood. The alkalinity 

 of human blood, based upon a study of the records of different observers, 

 may be taken as corresponding to 250 to 350 (mean 280) mg. of NaOH to 

 100 c.c. of blood. 



In the lower animals, Zuntz (Hermann's Handbuch der Physiologie, 

 1880, iv, 2 Th., 73; Beitriige z. Physiologie des Bluts, 1868, 13; Centralblatt 

 f. med. Wissensch., 1867, v, 801) found in a pig a value of 330 mg. of Na 2 C0 3 

 and in 10 dogs values ranging from 133 to 274 mg. of Na 2 CO 3 . In one ex- 



