THE LIFE-HISTORY OF THE LEUCOCYTE 271 



beneficial results have been obtained by this method of treat- 

 ment in cases of sympathetic ophthalmia, with restoration of 

 the blood picture to the normal — a result which constitutes 

 one of the greatest advances made in ophthalmic therapeutics 

 in recent years. 



Another disease, again, in which a relative large hyaline 

 mononuclear leucocytosis is usually stated to be present is 

 variola or smallpox, and this fact may add some weight to 

 the view that it is to the protozoa rather than to the bacteria 

 proper that we must eventually look for the causal micro- 

 organism of the disease. 



In making differential leucocyte counts it was shown by 

 Lucey that the percentage of large hyaline mononuclears tends 

 to vary according to the seat of origin of the drop of blood 

 taken for examination, and the method observed in spreading 

 the film. When, for example, blood is obtained by puncture 

 of the lobule of the ear, and the first or second drop obtained is 

 used for making the film, a much larger mononuclear leucocytosis 

 is found even in normal individuals than when blood is obtained 

 direct from veins, or by pricking a finger. If, however, the ear 

 be warmed, rubbed, or massaged before making a puncture, 

 and the first and second drops are discarded, this false leuco- 

 cytosis is not observed. Similarly, excessive squeezing of the 

 tissues should be avoided as this tends to raise the relative 

 lymphocyte, but not the larger hyaline, count. Lucey attributes 

 these findings to the concentration of the large hyaline leuco- 

 cytes in the capillaries of the ear, such concentration being due 

 to the slowing down of the circulation in this situation. Owing 

 to the immobility of this organ, to the absence of muscular 

 movements, and to its exposed position to cold, retardation of 

 the circulation is particularly liable to occur in the lobule of 

 the ear, which therefore should be avoided in obtaining blood 

 for differential leucocyte counts, unless the precautions 

 enumerated above are strictly observed. 



The consideration of the two varieties of leucocytes dealt 

 with in this communication by no means exhausts the possi- 

 bihties of the differential count. The remaining white blood 

 cells — namely, the lymphocytes large and small, the eosinophiles 

 and the basophiles, as well as the abnormal forms of leucocyte 

 found in various blood diseases — all provide interesting subjects 

 for study and investigation. 



The factors concerned in the life-histories of the various 

 leucocytes here considered have been drawn exclusively from 

 human sources. So far as I am aware but little work has been 

 done in this field with respect to animals either in health or 

 disease, and equally important and interesting results would 

 appear to await the worker who is prepared to apply similar 



