BLOOD. 



345 



in consequence the erythroblasts are again stimulated to greater activity. This 

 variation in haemoglobin with the altitude is an interesting adaptation which 

 ensures always a normal oxygen-capacity for the blood. 



Physiology of the Blood-leucocytes. The function of the blood-leuco- 

 cytes has been the subject of numerous investigations, particularly in connection 

 with the pathology of blood diseases. Although many hypotheses have been 

 made as the result of this work, it cannot be said that we possess any positive 

 information as to the normal function of these cells in the body. It must be 

 borne in mind in the first place that the blood-leucocytes are not all the same 

 histologically, and it may be that their functions are as diverse as is their mor- 

 phology. Various classifications have been made, based upon one or another 

 difference in microscopic structure and reaction. Thus, Ehrlich groups the leuco- 

 cytes according to the size and the staining of the granules contained in the cyto- 

 plasm, making in the latter respect three main groups : oxyphiles or eosinophiles, 

 those whose granules stain only with acid aniline dyes that is, with dyes in 

 which the acid part of the dye acts as the stain ; basophiles, those which stain 

 only with basic dyes; and neutrophiles, those which stain only with neutral 

 dyes 1 (Fig. 92). This classification is frequently used, especially in patholog- 







FIG. 92. Blood stained with Ehrlich's "triple stain" of acid-fuchsin, methyl-green, and orange G. 

 (drawn with the camera lucida from normal blood) (after Osier): a, red corpuscles; 6, lymphocytes; c, 

 large mononuclear leucocytes; d, transitional forms; e, neutrophilic leucocytes with polymorphous 

 nuclei (polynuclear neutrophiles) ; /, eosinophilic leucocytes. 



ical literature, but it is not altogether satisfactory, since no definite functional 

 relationship of the granules has been established ; and, moreover, it is unde- 

 cided whether or not the specific granules are permanent or temporary struc- 

 tures in the cells. A safer classification perhaps is the following: 1. Lympho- 

 cytes, which are small corpuscles with a round vesicular nucleus and very scanty 

 cytoplasm : they are not capable of amoeboid movements. These corpuscles are 

 so called because they resemble the leucocytes found in the lymph-gland, and 



1 For a recent discussion and modification of this classification see Kanthack and Hardy, 

 Journal of Physiology, vol. xvii., 1894, p. 81. 



