DEVELOPMENT OF LEUCOCYTES. 



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before breakfast ; an hour after breakfast, which was taken at 8 o'clock, 1 : TOO ; be- 

 tween 11 and 1 o'clock, 1:1500; after dining, at 1 o'clock, 1:400; two hours after, 

 1 : 1475 ; after supper, at 8 P. M., 1 : 550 ; at 11 p. M., 1 : 1200. The leucocytes are 

 much lighter than the red corpuscles, and, when the blood coagulates slowly, are fre- 

 quently found with a certain amount of colorless fibrin forming a layer on the surface of 

 the clot, which is called the " buffy-coat." 

 Their specific gravity is about 1070. 



Numerous observers, among whom may 

 be mentioned Donne, Kolliker, Gray, Hirt, 

 and Halassez, have noticed a great in- 

 crease in the number of leucocytes in the 

 blood coming from the spleen, and have 

 supposed that they are formed chiefly in 

 this organ. It is inconsistent with the 

 mode of development of these corpuscles 

 to suppose that any special organ is exclu- 

 sively engaged in their production; and 

 their persistence in animals after extirpa- 

 tion of the spleen shows that they are de- 

 veloped in other situations. 



The function of the leucocytes is not 

 understood. The supposition that they 



FIG. 6. Human red and while blood-corpwcles. 



break down and become nuclei for the de- 

 velopment of red corpuscles, which at one 

 time obtained, is a pure hypothesis, which has no positive basis in fact. 



Development of Leucocytes. These corpuscles appear in the blood-vessels very early 

 in foetal life, before the lymphatics can be demonstrated. They arise in the same way as 

 the red corpuscles, by genesis from materials existing in the vessels. They appear in 

 lymphatics, before these vessels pass through the lymphatic glands, in the foetus anterior 

 to the development of the spleen, and also on the surface of mucous membranes ; so 

 they cannot be considered as produced exclusively by the lymphatic glands, as has been 

 supposed. There is no organ nor class of organs in the body specially charged with their 

 formation ; and, although they frequently appear as a result of inflammation, this process 

 is by no means necessary for their production. Robin has carefully noted the phenom- 

 ena of their development in recent wounds. The first exudation consists of clear fluid, 

 with a few red corpuscles; then, a finely granular blastema. In from a quarter of an 

 hour to an hour, pale, transparent globules, from -g-^Vtr to WW f an m h m diameter, 

 make their appearance, which soon become finely granular and present the ordinary 

 appearance of leucocytes. They are thus developed, like other anatomical elements, by 

 organization of the necessary elements furnished by a blastema, and not by the action 

 of any special organ or organs. 



This view of the mode of development of leucocytes seems to be established by the 

 following very elegant experiments of Onimus, showing that corpuscles may be devel- 

 oped, under favorable conditions, in a perfectly clear, homogeneous blastema : 



Onimus used the clear fluid taken without delay from rapidly-developed blisters, 

 which he found ordinarily contained no leucocytes, but which he carefully filtered in 

 order to remove all sources of error. The filtered liquid contained no morphological 

 elements ; but, on the other hand, he found that, if the liquid were allowed to remain 

 for an hour or more in contact with the derma, it always contained leucocytes and epi- 

 thelial cells. Under these circumstances, even after filtration, the liquid contained a few 

 leucocytes ; but, after six or seven hours of repose in a conical vessel, the corpuscular 

 elements gravitated to the bottom, leaving the upper portion of the liquid perfectly clear. 



