COUNTING THE LEUKOCYTES 283 



the blood, in speaking of the hemoglobin test, are also true as regards the 

 blood-count. 



In practice the value of the determination of the number of red blood- 

 corpuscles is not very great, but it is important in any careful study of cases. 

 This is obvious if we realize that the amount of hemoglobin and the number 

 of blood-corpuscles are not always exactly proportional ; that, for example, a 

 diminution in the hemoglobin contents to 50 per cent, does not necessarily 

 imply a diminution of erythrocytes from 5,000,000 to 2,500,000 ; they may be 

 above or below this. We designate as the average "value" (V) of the indi- 

 vidual corpuscle -^, i. e., the division of the percental hemoglobin figure by 

 the percental diminution or increase of the erythrocytes. [" Color-index " is 

 the word generally used in America instead of " value." — Ed.] If, for exam- 

 ple, the amount of hemoglobin has been reduced to 50 per cent., the erythro- 

 cytes being '2,500,000 to the c.mm., the average "value" has remained 1 ; if, 

 however, with 50 per cent, hemoglobin only 200,000 red blood-corpuscles are 

 present, the V has even risen to 1.25 (|S). On the other hand, the 

 "value" is only 0.8 if we have only 40 per cent, hemoglobin and 2,500,000 

 red blood-corpuscles. This " value-estimation " is of importance for the rea- 

 son that the various types of anemic conditions are distinguished by the 

 " value " [or color-index] of the blood ; for example, in chlorosis or in post- 

 hemorrhagic anemia [or, in fact, in any well-marked secondary or symp- 

 tomatic anemia. — Ed.], V is often decidedly below 1, while in progressive 

 pernicious anemia it is frequently decidedly above 1. 



The number of red blood-corpuscles to the c.mm. upon the average amounts 

 in men to 5,000,000, in women to 4,500,000. [Ilewes and other Americans 

 have noted that in healthy American adults the number of red cells is usually 

 near 6,000,000, often above that figure. — Ed.] In most anemic conditions 

 this is reduced, and values below 1,000,000, even as low as 300,000, have been 

 seen without absolutely precluding the recovery of the patient. On the other 

 hand it must be emphasized that a normal number of erythrocytes is not 

 proof against the presence of anemia, unless the amount of hemoglobin is 

 also normal. 



Under certain circumstances, some of which have not yet been sufficientlj'' 

 explained, a decided increase of red blood-corpuscles occurs, a hyperglobulia. 

 This is, for example, the case in the various forms of stasis of the circulation, 

 but it is also the expression of an actual increase of blood formation. Under 

 such circumstances, Tlirk, for instance, found 9,150,000 erythrocytes. 



[Cases of this type were first described by Cabot in 1899, later by Osier who 

 noted particularly the enlargement of the spleen associated with the poly- 

 cythemia. — Ed.] 



III. COUNTING THE LEUKOCYTES 



To count the white blood-corpuscles we use a dilution of only 1 to 10, 

 which may be done in the large-bore mixing pipette in the Thoma apparatus. 

 In order that counting may be facilitated the red blood-corpuscles are 



