114 PHYSIOLOGY CHAP. 



The varying character of the protoplasm and nucleus make it 

 possible to distinguish several kinds of leucocytes. From their 

 size, and probably from their various grades of development, 

 Schultze recognised three varieties ; the smallest attain at most a 

 diameter of 5 //. and possess a large nucleus, the medium have an 

 average of 7 p, the largest of 9 /A ; the latter are often uiultinuclear 

 and of irregular external shape. In the foetus of less than four 

 months there are still larger ones which may reach 15-19 ^ (Fig. 40). 



According to a more rational classification proposed by Ehrlich 

 and Engel, leucocytes are divided into two classes : those with 

 and those without granules. The leucocytes with granules are 

 distinguished as mononuclear and polynuclear, and by their 

 staining affinity, as acidophile, neutrophile, and basophile. 



Mononuclear leucocytes with granules are extremely rare, or 

 entirely absent, in normal circulating blood ; according to many 

 authors they represent the transition forms to polynuclear 

 correspondents. Polynuclear neutrophile leucocytes constitute 

 the greater part of the white corpuscles (from 4j- to f ) ; they have 

 a diameter of 9-10 p, exhibit lively amoeboid movements, and 

 perform the function of phagocytosis. Polynuclear leucocytes 

 with fine or coarse acidophile granulations are very scarce 

 (from 2 per cent to 4 per cent). Still rarer in the circulating 

 blood are those with basophile granulations (0*5 per cent) ; they 

 are found almost exclusively in the tissues of the haematopoietic 

 organs. 



The non-granular leucocytes are distinguished as lymphocytes, 

 large lymphocytes, large mononuclear cells and inflammatory 

 forms. The lymphocytes are the size of normal erythrocytes, with 

 a reticular nucleus which occupies nearly the whole cell. They 

 represent about -J- the total number of white corpuscles; their 

 number varies not merely in certain physiological conditions, as 

 for instance in digestion, but also in pathological states. 



The large lymphocytes, large mononuclear cells, and in- 

 flammatory forms have precisely similar characters to the pre- 

 ceding ; they are differentiated by the volume of their protoplasm. 

 These cells are comparatively rare in normal blood, and are more 

 interesting to the pathologist than to the physiologist. 



Many clinical, anatomical, and experimental researches have 

 been directed to the object of establishing the relations existing in 

 last resort between the lymphocytes and the granular leucocytes 

 with polymorphous nuclei, as well as the general relations 

 between the various white morphological elements of the blood. 

 Here we must only say that while Ehrlich's theory admits a sharp 

 distinction between the cells derived from the lymphatic system 

 and those derived from bone-marrow, there is another opposing 

 theory, according to which the lymphocytes are the young cells 

 which give rise to all other elements of the blood (Ouskoff). 



