Microscopic Examination of Blood. 315 



vary in size exceedingly, some being smaller than the aver- 

 age coloured corpuscle, while others are more than twice as 

 large. 



Number. — The number of leucocytes in each cubic milli- 

 meter of normal blood varies widely in the same individual at 

 different times of the day, and from day to day. From a 

 number of observations made by myself with great care, I am 

 led to take from 6,000 to 10,000 as the average in health, — 

 rather a wide range. Limbeck, as cited, on page 134, gives 

 the collated results of various estimates, ranging from 4,800 

 to 10,590. Osier, Principles and Practice of Medicine, 1892, 

 page 699, takes 6,000 as the average in health. I think this 

 estimate rather low. 



JVuclei. — As mentioned before when describing the varieties 

 of leucocytes, the number of nuclei varies, some leucocytes con- 

 taining; a sincrle nucleus, others beincr multinuclear. Schafer, 

 in Quain's Anatomy, 1 speaking of the nuclei of leucocytes, 

 says, "Thus a nucleus not unfrequently becomes elongated 

 and either irregular in outline or folded on itself, so that when 

 the ends are turned up, the appearance of two nuclei is pro- 

 duced, where in reality there may be but one. In fact the 

 occurrence of several nuclei in the pale corpuscle is much 

 more rare than is generally supposed, for it will be usually 

 found that even when there appear to be several nuclei 

 in a corpuscle they are united together by long strands of 

 chromoplasm." 



This is not in accordance with my observations; for, during 

 an investigation of the nuclei of leucocytes of normal blood, 

 undertaken in the fall of 1892, I found by staining that many 

 leucocytes were multinuclear. This accords with what has 

 been observed previously, as before quoted from Osier, who 

 gives the polynuclear as 65 to 80 per cent, of all leucocytes. 

 Probably in this estimate transitional forms were included. 



' Quain's Elements of Anatomy. Longmans, Green & Co., London and 

 New York. Tenth Edition. 1891. Vol. L, Part IL, p. 214. 



