THE BLOOD. 



253 



estimated at from 5000 to 10,000, though the average is about 7500. The 

 number, however, is influenced by a variety of physiologic conditions. The 

 ingestion of food rich in protein material raises the count from 30 to 40 per 

 cent., as compared with the count before the meal. In the new-born the 

 number is greater than in adults 17,000 to 20,000 per cubic millimeter. 

 Cabot states that 30,000 is never a high count after a meal in infants under 

 two years. In the later months of pregnancy, especially in primiparae, the 

 number increases to 16,000 to 18,000. Many pathologic conditions of the 

 body also influence the count very considerably. 



Fasting for a few days always lowers the count, and in a case of total 

 abstinence of food for a week, reported by Luciani, the count fell to 86 1 per 

 cubic millimeter, after which it rose to 1530, where it practically remained 

 for the succeeding three weeks of the fasting period. 



When the number of leukocytes present in the peripheral blood exceeds 

 the normal, i.e., 10,000 per cubic millimeter the condition is termed leuko- 



FIG. 113. AMCEBOID MOVEMENTS OF A WHITE CORPUSCLE FROM THE FROG. The form 

 changes occurred within ten minutes. The black particles are Chinese ink which had been 

 injected twenty-four hours before into the dorsal lymph sac. (Rauber-Kopsch.) 



cytosis; when the number falls below the normal the condition is termed 

 leukopenia. Both conditions, however, may be only temporary and therefore 

 physiologic, or they may be permanent, associated with certain diseased states 

 of the body and therefore pathologic. It is therefore permissible to speak 

 of a physiologic and a pathologic leukocytosis and leukopenia. 



The method for counting the white corpuscles is similar to that used in 

 counting the red corpuscles. The given volume of blood should, however, 

 be diluted with 10 or 20 volumes of a one per cent, solution of acetic acid, 

 which disintegrates the red corpuscles and thus facilitates the counting of 

 the white. The pipette should have a larger bore than that used for the 

 red, and a much greater number of squares in the counting chamber should 

 be counted, so as to dimmish the percentage of error. 



Physiologic Properties. The white corpuscles and especially the 

 leukocytes possess the characteristic property of exhibiting movements 

 similar to those observed in the amoeba, and are therefore termed amoeboid. 

 These movements consist in alternate protrusions and retractions of portions 

 of the cell body, as a result of which they exhibit a great variety of forms. 



