BLOOD. 171 



This method is objectionable, not merely on account of the 

 time and labour required for its various stages, but further, 

 because the whole of the water cannot be estimated by the in- 

 dicated process. Moreover, the quantity of the hcematoglobulin 

 which is dependent upon the quantity of blood-corpuscles, will 

 be given in excess, as it is certain that the whole of the serum 

 cannot be separated from the clot, in the manner proposed by 

 Denis. The determination of the fibrin may also be inac- 

 curate in consequence of the continuous treatment of the clot 

 with water, which has the effect of transforming a portion of it 

 (i. e. the fibrin) into minute flocculi or granules which combine 

 with a viscid substance. The estimation of the fat and of the 

 extractive matters is also very inaccurate ; the quantity of fat 

 given by Denis in his analyses being much too large, and of 

 extractive matter, too small. Finally, no certain results with 

 respect to the separation of the salts can be obtained by this 

 method. Whatever may be the faults of his process, he is at 

 least deserving of praise for having conducted no less than 

 eighty-three analyses in this laborious manner. 



The method that I pursue in the analysis of the blood, if 

 not strictly correct, at least gives results that approximate nearer 

 to the truth than those of Denis. In explaining it, I must enter 

 a little into detail, in order to indicate certain necessary pre- 

 cautions, and to explain on what points it is deficient. 



a. I receive two, three, or at the most four ounces of blood, 

 as it flows from the vein, in a thin glass, and stir it,^ but not 

 "violently, till the fibrin separates. If it be stirred too vio- 

 lently, a portion of the fibrin becomes separated in the form of 

 finely-divided scum, which cannot be easily collected. When 

 the blood has completely cooled, it is weighed, together with 

 the rod and glass, in a good balance ; it is then poured out, 

 the glass is cleansed and dried, the rod is freed from the ad- 

 herent fibrin, and is washed and dried : the glass and rod are 

 then weighed, and the quantity of blood determined. 



h. Any fibrin that separates in flocculi from the blood must 

 be collected, added to the former, pressed, and placed in water. 

 If the water become strongly coloured, it must be poured off" 



' [A bunch of fine twigs is generally used for this purpose, but the fibrin may be 

 obtained with as much accuracy by shaking the blood in a stoppered bottle containing 

 a few fragments of lead, to which it readily adheres.] 



