420 BLOOD AND LYMPH. 



the amount of alkali in the blood available for the protection of 

 the reaction, or as it is frequently expressed, a diminution in the 

 alkaline reserve of the body. Such a condition is designated as 

 "acidosis," although the reaction of the blood is still alkaline. 

 Two relatively simple reactions have been suggested to test for the 

 existence of "acidosis." One is to determine the capacity of the 

 blood-plasma to absorb CO 2 under a given pressure. The normal 

 CO 2 capacity is from 50 to 60 per cent, and a decided fall below this 

 level indicates a diminution in alkali in the blood. The second is to 

 ascertain the amount of. sodium bicarbonate given by mouth that 

 suffices to give an alkaline reaction to the urine. In acidosis more 

 carbonate will be required to give this result.* 



Specific Gravity. The specific gravity of human blood in the 

 adult male may vary from 1.041 to 1.067, the average being about 

 1.055. The most satisfactory method of determining this factor is, 

 of course, to compare the weight of a known volume of blood with 

 that of an equal volume of water, but for observations upon human 

 beings such small quantities of blood must be used that recourse must 

 be had usually to a more indirect method. Perhaps the simplest of 

 the methods suggested is that devised by Hammerschlag. t In this 

 method a mixture is made of chloroform (sp. gr., 1.526) and benzol 

 (sp. gr., 0.889). The mixture is made in such proportions as to 

 have a specific gravity of about 1.055. A drop of blood from the 

 finger is shaken into this mixture; if the drop sinks to the bottom 

 it is evident that the specific gravity of the blood is higher than that 

 of the mixture, and the reverse is true if the drop rises. By adding 

 more of the chloroform or of the benzol, as the case may be, the 

 specific gravity of the mixture may be quickly altered so as to be 

 equal to that of the drop of blood, which will then float in the liquid 

 without a distinct tendency to rise or fall. The specific gravity of 

 the mixture, which is also that of the blood, is then determined by a 

 suitable hydrometer. By the use of such methods it has been found J 

 that the specific gravity varies with age and with sex; that it is 

 diminished after eating and is increased after exercise; that it has a 

 diurnal variation, falling gradually during the day and rising slowly 

 during the night; and that it varies greatly in individuals, so that 

 a specific gravity which is normal for one may be a sign of disease 

 in another. The specific gravity of the corpuscles is slightly greater 

 than that of the plasma. For this reason the corpuscles in shed 

 blood, when its coagulation is prevented or retarded, tend to settle 

 to the bottom of the containing utensil, leaving a more or less clear 



* See L. Henderson, "Science," July 27, 1917; Sellards, "The Principles of 

 Acidosis," 1917; and Van Slyke and Cullen, Loc. cit. 



t Hammerschlag, "Zeitschrift f. klin. Med.," 20, 444, 1892. 

 J See Jones, "Journal of Physiology," 12, 299, 1891. 



