VARIETIES OF LEUCOCYTES. 423 



longed, seems to increase their number in the blood (9, 10); 

 perhaps this accounts for their greater frequency in the 

 blood of winter than of summer frogs. They are present 

 in the blood of the foetus from an early period of intra- 

 uterine life. They are especially numerous in bone mar- 

 row, and it has been urged by Ehrlich that those in the 

 blood come from the bone marrow. Kanthack has, how- 

 ever, shown that they can increase enormously in a limb 

 from which all bone marrow has been removed ; and it 

 must be remembered that large islets of them occur also in 

 the mesentery ; that they can be found forming an almost 

 unbroken sheet in the capsules of many lymphatic glands ; 

 and that they crowd the choroid plexuses of the cerebral 

 ventricles (18). They are numerous also in the mucosa of 

 the small intestine, and it is said especially so after chemical 

 irritation of the membrane. Nevertheless, in view of their 

 resemblance in many microchemical reactions to the sub- 

 stance composing chromocytes, it is interesting to find them 

 especially abundant in the very tissue which is most concerned 

 with the production of chromocytes, i.e., the red marrow. 



Some investigators, among them M. Heidenhain, look 

 upon the coarsely granular oxyphil leucocyte as a cell 

 undergoing degeneration or over- ripe. Apparently the 

 character of the granulation of the cell-body inclines them 

 to this view, by the same line of argument as we may 

 sometimes legitimately follow when judging a cell to be 

 degenerating because it contains fatty granules in it. It is 

 noteworthy that the opinion is shared chiefly by those 

 whose papers deal only with the morphological characters 

 of the cell, and with it in preparations hardened and 

 stained. It cannot, I think, be shared by any one 

 who has studied the cell alive and active on the warm 

 stage or in transparent tissues. To those who are ac- 

 quainted with it under approximately normal conditions 

 such a view is negatived most emphatically by the robust 

 reactions and the high resistance to adverse conditions, e.g. y 

 irrigations with weak and strong salines, etc., exhibited by 

 the cell. Although there is every reason for rejecting the 

 view that the oxyphil leucocyte is a degenerated or over- 



