522 BLOOD-CORPUSCLES IN [SECT. 221. 



above the average in men and youths after a diet rich in albumen 

 (they then reach to 3-5 in a 1000), in pregnant females (3*6), 

 menstruating women (4*0), and in boys (4-5). In fasting animals, 

 as Heumann has also observed in pigeons, they decrease ; and after 

 long fasting they even disappear entirely, at least in frogs, though, 

 on the other hand, De Pury found their relative numbers to be 

 increased after three weeks of low diet and fasting. Very remark- 

 able is their increase in numbers, not only relatively but absolutely, 

 after venesections, and this may go to such a length in the case of 

 the horse (of course after enormous evacuations of blood, up to 

 fifty pounds), that the coloured and colourless corpuscles appear 

 equally numerous. — The colourless corpuscles are lighter than the 

 coloured, and are, accordingly, found in greater quantities in the 

 upper strata of the crassamentum. If the latter possesses a buffy 

 coat, a large number of such corpuscles are always found in it, 

 especially when their number in the blood has been increased by 

 previous venesections ; hence, in such cases, they may even con- 

 stitute the half of the buffy coat (Pemak, Donders). Their small 

 tendency to sink partly results also from the circumstance, that, 

 although they are provided with uneven surfaces and are disposed 

 to cohere to each other, they nevertheless rarely form any 

 large heaps, and never rouleaux. In leucaemia, the colourless 

 blood-cells are remarkably increased in number, so that they have 

 been found by De Pury in the proportion of one to only seven to 

 twenty-one of the red corpuscles. In ague, even though there be 

 enlargement of the spleen, Hirt finds the colourless cells reduced in 

 amount. By the operation of tonic remedies (myrrh, iron,. quinine), 

 the number of the colourless cells may be notably increased, 

 according to Hirt, even in half an hour. 



Conditions of the Blood-corpuscles in different hinds of Blood. — 

 Sensitive as the blood-cells are to different re-agents outside the 

 body, their appearance within it is remarkably constant, at least 

 as regards their form. Within the limits of physiological con- 

 ditions, no considerable and permanent differences of them are to 

 be detected ; in the arterial and venous blood, and in various sorts 

 of blood in different organs, they exhibit an almost uniform aspect : 

 and not only is this the case, but even in the most diverse diseases 

 no visible alterations present themselves. And yet it cannot be 

 doubted that the forms of the blood-cells, like the colour and 

 chemical composition of the blood, are subject to certain variations 

 and changes, according as the blood is more concentrated or diluted, 

 and according as it contains more or less of certain salts and other 

 substances. This change of form, however, is so trifling, that it is 



