COMPOSITION OF THE BLOOD. 299 



Female than in the Male. Much is probably yet to be learned, regard- 

 ing the influence of different kinds .of food recently taken, on the pro- 

 portion of these constituents of the blood ; and it does not seem unlikely, 

 from what has been already stated ( 517), that the quantity of fatty 

 matter is especially liable to variation, in accordance with the amount 

 contained in the food, and the time which has elapsed since the last 

 meal. 



528. The Saline constituents of the blood, obtained by drying and 

 incinerating the whole mass, usually amount to between 6 and 7 parts 

 in 1000. More than half of their total quantity is composed of the 

 Chlorides of Sodium and Potassium ; and the remainder is made up of 

 the tribasic Phosphate of Soda, the Phosphates of Lime and Magnesia, 

 Sulphate of Soda, and a little Phosphate and Oxide of Iron. Of 

 these the chief part are dissolved in the Serum ; but the Earthy Phos- 

 phates, which are insoluble by themselves, are probably combined with 

 the proteine-compourids ( 175); and the Iron is contained, chiefly or 

 entirely, in the red corpuscles. It is difficult to speak with certainty, 

 from the examination of the ashes of the blood, as to the state of the 

 saline contituents of the circulating fluid. Thus, the Serum has an 

 alkaline reaction ; and this has been supposed to be due to the pre- 

 sence of alkaline Carbonates. Moreover, the presence* of the Lactates 

 of potash and soda seems probable ; for it is certain that lactic acid is 

 normally introduced into the blood, and is also eliminated from it; 

 and the rapidity with which the lactates are removed as such, or are 

 converted into carbonates, seems to afford a sufficient explanation of 

 the difficulty in 'demonstrating the presence of this acid in the circu- 

 lating fluid. Although the ashes of the entire mass of blood do not 

 effervesce on the addition Of an acid, effervescence takes place, when 

 acid is added to the ashes of the Serum ; showing the existence in it, 

 either of alkaline Carbonates, or- of Lactates which have been reduced 

 to the state of Carbonates by incineration. When the entire mass of 

 blood is incinerated, however, enough phosphoric acid is produced from 

 the phosphorized fats, to neutralize the alkaline carbonates, and thus to 

 prevent their presence from being recognised. The alkaline reaction of 

 the blood, however, is certainly dependent in part upon the presence of 

 the tribasic phosphate of soda, which appears to confer upon the serum 

 a special power of absorbing carbonic acid. 



529. The following appear, from the considerations stated in the pre- 

 ceding part of the Volume, to be the chief uses of the principal consti- 

 tuents of the Blood, in the general economy. The Fibrine is the material, 

 which is most completely prepared for organization, and which supplies 

 what is requisite for the nutrition of the larger proportion of the solid 

 tissues of the body. It is, therefore, being continually withdrawn from 

 the blood by the nutritive operations ; and the demand appears to be 

 supplied, in part by the influx of Fibrine that has been prepared in the 

 Absorbent system, and in part by the continued transformation of Albu- 

 men, which takes place during the circulation of the Blood. If a proper 

 amount of Fibrine be not present in the Blood, its physical properties 

 are so far altered, by the diminution of its viscidity, that it will not 

 circulate through the capillaries as readily as before ; a certain degree 



