OSMOTIC PRESSURE OF THE SERUM. 263 



exists a rather close "correspondence between human and animal blood- 

 serum, and it is therefore sufficient to give here the analysis of C. SCHMIDT l 

 of (1) human blood, and BUNGE and ABDERHALDEN'S analyses (2) of 

 serum of ox, bull, sheep, goat, pig, rabbit, dog, and cat. The results 

 correspond to 1000 parts by weight of the serum. 



i 2 



K 2 O 0.387-0.401 0.226-0.270 



Na 2 4.290-4.290 4.251-4.442 



Cl 3.565-3.659 3.627-4.170 



CaO 0.155-0.155 0.119-0.131 



MgO 0.101 0.040-0.046 



P 2 O 5 (inorg.) 0.052-0.085 



Even if we bear in mind that certain bodies, such as carbon dioxide* 

 are driven off during incineration, and that other bodies, such as sul- 

 phuric acid and phosphoric acid, are formed from sulphurized and 

 phosphorized organic substances, still quantitative analyses like the above 

 are not sufficient for the scientific demands of to-day. They do not 

 show the true composition, and especially do not give an explanation 

 of the number of different ions present in the serum or in other fluids, a 

 question which is of the greatest physiological importance. An answer 

 to these questions is obtainable only by physico-chemical investigations, 

 which have thus far been used chiefly in determining the molecular 

 concentration, the amount of electrolytes and non-electrolytes, and the 

 degree of dissociation. 



The average depression of the freezing-point of mammalian blood 

 corresponds, as already given in Chapter II, closely to a 9 p. m. (J= 

 0.551-0.561) solution of common salt, and at the present time such a 

 solution is considered as a physiological salt solution for man and other 

 mammalia. In lower animals and fish the conditions are otherwise, 

 as shown in the above-mentioned chapter. 



There are recorded a great number of investigations on the changes 

 in the osmotic pressure or the molecular concentration of the blood- 

 serum under various physiological conditions as well as in disease, but 

 still it is no doubt too early to draw any definite conclusions from these 

 observations. 



The degree of dissociation (see Chapter II) of sera has been determined 

 by several investigators, and according to HAMBURGER 2 it lies between 

 0.65 and 0.82. The molecular concentration, which represents the 

 total number of molecules and ions per liter is, according to BURGARSKY 

 and TANGL, on an average of about 0.320 mol. per liter. They also 



1 Cit. from Hoppe-Seyler, Physiol. Chem., 1881, p. 439. 



2 Osmotisher Druck und lonenlehre, Wiesbaden, 1902-1904, where the literature 

 on the physical chemistry of the blood can be found. 



