336 VEHICLES OF CHEMICAL CORRELATION 



protein and containing in fact all of the constituents of the plasma with 

 the exception of the formed elements and the protein Fibrinogen, 

 from which the fibrin arose. This fluid is termed the Serum, and it 

 may be obtained in greater abundance and more rapidly by removing 

 the fibrin from freshly shed blood by whipping it with glass rods or by 

 shaking it up with beads. The fibrin adheres in long strings to the rods 

 or beads and may be removed with them from the fluid which is now 

 termed Defibrinated Blood. From this the corpuscles, red and white, 

 may be removed by centrifugalization, the supernatant fluid consisting 

 of serum. 



The relative volumes of the plasma and corpuscles may be deter- 

 mined in several ways of which the most accurate is probably the 

 method devised by Hoppe-Seyler, which suffers from the disadvantage, 

 however, of being somewhat lengthy and tedious. Defibrinated blood 

 is employed for the estimation, the removal of fibrin from the whole 

 blood introducing only a very slight error which, if desired, may be 

 separately estimated. Three determinations are made, namely: 

 (a) The total protein including hemoglobin in 1000 grams of whole 

 blood, (b) The total protein, including hemoglobin, in the blood- 

 corpuscles derived from 1000 grams of blood by centrifugalization 

 followed by repeated washing with isotonic salt solution, until the 

 washings are free from protein, (c) The total proteins in 1000 grams 

 of serum free from corpuscles. The difference between (a) and (6) 

 yields the proteins in the serum contained in 1000 grams of blood, 

 so that the ratio ~ yields the proportion of 1000 grams which is 

 constituted by the serum in that weight of whole blood. For example, 

 in an actual estimation, the total protein in a kilogram of blood 

 amounted to 172.9 grams, while the corpuscles from this amount of 

 blood contained 124.0 grams of protein. The serum in a kilo- 

 gram of blood, therefore, contained 172.9 124.0 = 48.9 grams of 

 protein. One kilogram of serum, however, contained 72.5 grams 

 of protein. Therefore the serum in a kilogram of blood comprised 

 HT ths of a kilogram or 674.5 grams. The Serum (or plasma as 

 it is termed before the fibrin is removed from the blood) therefore 

 forms about two-thirds of the whole blood and the corpuscles one-third. 

 This proportion is, however, subject to very wide variations. The blood- 

 count itself, i. e., the number of corpuscles contained in a cubic milli- 

 meter of whole blood, is variable and in conditions of Anemia may fall 

 to one-half the normal value. Then the volume occupied by the indi- 

 vidual corpuscles varies with the osmotic pressure of the serum, hyper- 

 tonicity involving shrinkage and hypotonicity involving dilation of 

 the corpuscles. 



The Electrical Conductivity of the whole blood compared with that of 

 the serum derived from it may also be employed, as Stewart has shown, 

 for the determination of the relative volumes of the corpuscles and 

 serum. The results yielded by this and by other methods are in 

 substantial agreement with those furnished by the method of Hoppe- 

 Seyler. 



