VARIATIONS OF BLOOD. 83 



or generally in the blood, including casein, especially in 

 women during lactation : glucose, or grape-sugar, found in 

 the blood of the hepatic vein, but disappearing during its 

 transit through the lungs (Bernard); urea, and in very 

 minute quantities, uric acid (Garrod) ; hippuric and lactic 

 acids ; ammonia (Richardson) ; and lastly, certain colouring 

 and odoriferous matters. 



Variations in healthy Blood under different Circumstances. 



As the general condition of the body depends so much 

 on the condition of the blood, and as, on the other hand, 

 anything that affects the body must sooner or later, and 

 to a greater or less degree, affect the blood also, it might 

 be expected that considerable variations in the qualities of 

 this fluid would be found under different circumstances of 

 disease ; and such is found to be the case. Even in health, 

 however, the general composition of the blood varies con- 

 siderably. 



The conditions which appear most to influence the com- 

 position 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 being 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 de- 

 ficiency of red corpuscles. The quantity of white corpuscles, 

 on the other hand, and of fibrin, is increased. 



3. Age. From the analysis of Denis it appears that the 

 blood of the foetus is very rich in solid matter, and espe- 

 cially 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. 



G 2 



