440 BLOOD AND LYMPH. 



lymphocytes and the leucocytes, — and each of these into two or 

 more subgroups. Thus: 



I. Lymphocytes. No granules in the cell substance, and, though capable of 

 ameboid changes of form, this property is not characteristic and prob- 

 ably not sufficient to cause locomotion. 



(a) Small lymphocytes are about the size of the red corpuscles; the nu- 

 cleus is large, symmetrically placed, stains homogeneously, and the 

 cytoplasm is reduced to a very smaU amount. They form from 20 

 to 25 per cent, of all the white corpuscles. 



(6) Large lymphocytes. Two to three times as large as the preceding. 

 Nucleus somewhat eccentric; the cytoplasm is relatively more 

 abundant than in a, but non-granular. These forms exist only in 

 small numbers, forming 1 per cent, or less of the white corpuscles. 

 II. Leucocytes. Granules of different sorts found in the cytoplasm. Cells 

 characteristically ameboid. 



(a) Transition, /or ws (uninuclear leucocytes). Single large nucleus, more 

 or less lobulated; cytoplasm abundant and faintly granulated. The 

 granules stain with neutral dyes and are therefore designated as 

 neutrophile granules. The name, transition form, impli'^s that these 

 leucocytes represent an intermediate stage between the large lympho- 

 cytes and the following variety, but this belief is vigorously denied 

 by many competent hematologists. A recent view holds that these 

 cells arise from the capillary endothelium. They are actively 

 phagocytic and constitute from 2 to 10 per cent, of the total number 

 of white corpuscles. 



(b) Polynuclear or polyrnorphoniiclear leucocytes. The nucleus is seg- 

 mented into lobes connected by narrow strands. The cytoplasm 

 is especially ameboid and is granular. The granules in most cases 

 are neutrophilic and small in size. The typical cells of this kind 

 form the bulk of the white corpuscles of the blood — 60 to 7.5 per 

 cent. Eosinophilic leucocytes form a subgroup of this variety. 'I"hey 

 have a similar segmented nucleus, but the cytoplasm contains nu- 

 merous coarse granules that stain in acid dyes, such as eosin, whence 

 the name. 



(c) Mast cells. These peculiar cells exist in very small numbers under 

 normal conditions, — less than 1 per cent, of the total number of 

 white corpuscles. Thpy have a polymorphic nucleus like the pre- 

 ceding group, but differ in the fact that the granules in the cyto- 

 plasm are strongly basophilic, — that is, will stain only with basic 

 dyes, such as thionin. 



Current opinions vary greatly in regard to the origin and 

 relations of these different forms of white blood-corpuscles, almost 

 every writer proposing some special hypothesis to indicate his 

 particular point of view.* In general, however, it may be said 

 that the divergent views fall under two heads. First, the so- 

 called dualistic theory, according to which there are two sources 

 of origin for these cells, namely, the lymphohlasts of the lymph 

 nodes which give rise to the small lymphocytes and the myeloblasts 

 of the bone-marrow, which give rise to the granular leucocytes of 

 the blood. Second, the unitarian or monophyletic theory, ac- 

 cording to which all the white blood-corpuscles arise from a single 



* See Weidenreich for summary, "Ergebnis.se der Anatomic und Entwickel- 

 ungsgeschichte," vol. 19, part ii (1909), 1911; and Drinker, "The Pathological 

 Physiology of Blood-cell Formation and Blood-cell Destruction," O.xford Med- 

 icine, 1920. 



