18 



THE BLOOD. 



HaBmatine may be produced by decomposition of hsemaglobine, by a process which 

 it is not necessary to describe, as the hsematine is not a proximate principle. Hsematoi- 

 dine is also a product of decomposition of hgemaglobine, but it does not contain iron. 

 Hsematoidine is more interesting, however, from the fact that it is frequently found in 

 old clots that have been long extravasated in the tissues. Eobin found a notable quan- 

 tity of crystals of ha3matoidine in a cyst of the liver. 



Assuming, as we certainly may, that the 

 blood furnishes material for the nourishment 

 of all the tissues and organs, we should ex- 

 pect to find entering into its composition all 



/ rH" >T /9 the proximate principles existing in the body 



N iSN>,, ^ L...J'<-J //^ which undergo no change in nutrition, like 



the inorganic principles, and organic matters 

 capable of being converted into the organic 

 elements of every tissue. Farthermore, as 

 the products of waste are all taken up by the 



blood before their final elimination, these also 



x\ n ^'^ should enter into its composition. With these 



v\ Itf-'f * ^ facts in our minds, we can readily appreciate 



the importance of accurate proximate ana- 

 lyses of the circulating fluid. 



Notwithstanding the immense amount of 

 labor bestowed by the most eminent chemists 

 of the day upon the quantitative analysis of 

 the blood, and the great physiological interest 

 attaching to every advance in our knowledge 

 in this direction, the chemical difficulties in- 

 volved are so great, that even now there are 

 no analyses which give the exact quantities 

 of each of its inorganic constituents. This is 

 owing to the great difficulty in the analysis of 

 any fluid in which inorganic and organic prin- 

 ciples are so closely united ; for there is no 

 more delicate problem in analytical chemistry 

 than the determination of the presence and the 

 proportions of inorganic substances united with 



organic matter. Of the animal fluids which are easily obtained, the blood, from the large 

 proportion of different organic principles which enter into its composition, presents the 

 greatest difficulties to the analytical chemist. Another difficulty is the necessity of a 

 proximate, and not an ultimate analysis. It is not sufficient to give the amount of cer- 

 tain chemical elements which the blood contains; we must ascertain the amount of 

 these elements in the state of union with each other to form proximate principles. 



Most of the constituents of the blood are found both in the corpuscles and plasma. 

 It is difficult to determine all of the different constituents of these two parts of the blood. 

 It has been shown, however, by Schmidt, of Dorpat, that the phosphorized fats are more 

 abundant in the globules, while the fatty acids are more abundant in the plasma. The 

 salts with a potash-base have been found by the same observer to exist almost entirely 

 in the corpuscles, and the soda-salts are four times more abundant in the plasma than in 

 the corpuscles. In addition to the nutritive principles, \ve have, entering into the com- 

 position of the blood, urea, cholesterine, urate of soda, creatine, creatinine, and other 

 substances the characters of which are not yet fully determined, belonging to the class 

 of excrementitious principles. Their consideration comes more appropriately under the 

 head of excretion, and they will be fully taken up in the chapters devoted to that subject. 



FIG 1. Crystallised hcemaglobine. (Gautier.) 

 a, ft, crystals from the venous blood of man ; c, blood 

 of the cat ; d, blood of the Guinea pig ; , blood 

 of the marmot ; /, blood of the squirrel. (Gau- 

 tier.) 



