86 HAND-BOOK OF PHYSIOLOGY. 



freed from its salts, and is precipitated by solutions Of metallic salts, e.g. , 

 of mercuric chloride, copper sulphate, lead acetate, sodium tungstate, etc. 

 If dried at a temperature over 167 F. (75 0.) the residue is insoluble 

 in water, having been changed into coagulated proteid. 



P. Paraglobulin can be obtained as a white precipitate from cold serum 

 by adding a considerable excess of water and passing through it a current 

 of carbonic acid gas or by the cautious addition of dilute acetic acid. It 

 can also be obtained by saturating serum with crystallized sulphate mag- 

 nesium or chloride sodium. When obtained in the latter way precipita- 

 tion seems to be much more complete than by means of the former 

 method. Paraglobulin belongs to the class of proteids called globulins. 



The proportion of serum-albumin to paraglobulin in human blood 

 serum is as 1'511 to 1. 



The salts of sodium predominate in serum as in plasma, and of these 

 the chloride generally forms by far the largest proportion. 



Fats are present partly as fatty acids and partly emulsified. The 

 fats are triolein, tristearin, and tripalmitin. The amount of fatty matter 

 varies according to the time after, and the ingredients of, a meal. Of 

 cliolesterin and lecithin there are mere traces. 



Grape sugar is found principally in the blood of the hepatic vein,, 

 about one part in a thousand. 



The extractives vary from time to time; sometimes uric and hip- 

 puric acids are found in addition to urea, kreatin and kreatinin. Urea- 

 exists in proportion from *02 to *04 per cent. 



The yellow pigment of the serum and the odorous matter which gives 

 the blood of each particular animal a peculiar smell, have not yet been 

 properly isolated. 



VARIATIONS IN HEALTHY BLOOD UNDER DIFFERENT CIRCUMSTANCES. 



The conditions which appear most to influence the composition of the 

 blood in health are these: Sex, Pregnancy, Age, and Temperament. The 

 composition of the blood is also, of course, much influenced by diet. 



1. Sex. The blood of men differs from that of women, chiefly in be- 

 ing of somewhat higher specific gravity, from its containing a relatively 

 larger quantity of red corpuscles. 



2. Pregnancy. The blood of pregnant women has a rather lower 

 specific gravity than the average, from deficiency of red corpuscles. The 

 quantity of white corpuscles, on the other hand, and of fibrin, is in- 

 creased. 



3. Age. It appears that the blood of the foetus is very rich in solid 

 matter, and especially in red corpuscles; and this condition, gradually 

 diminishing, continues for some weeks after birth. The quantity of solid 

 matter then falls during childhood below the average, again rises during 

 adult life, and in old age falls again. 



