METHOD OF ANALYZING THE BLOOD. 3 



of serum, and evaporate upon the chloride of calcium hath until it ceases to lose 

 weight. The water, solid residue, and fixed saline constituents in 1000 parts of scrum 

 may be ascertained in a manner exactly similar to that by which these ingredients 

 were determined in 1000 parts of blood. 



From the numbers now obtained, the proportion of solid matters of the serum of 

 1000 parts of the blood may be calculated in the following manner: Knowing the 

 quantity of water in 1000 parts of blood, and assuming that this water exists 

 wholly in the form of serum; knowing also the amount of water and solid matter 

 contained in a given portion of serum; we may, from the quantity of water in the 

 blood, estimate the quantity of solids held in solution in the serum, thus:— 



Weight of water -> ( Weight of solid ) ( Water in } f Solids of serum 



in the quantity of I : ] matter in the quantity [ : : ] 1000 parts \- -j in 1000 parts 



serum employed ) ( of serum employed ) (of the blood) (of the blood. 



This is not absolutely correct, and all physiological chemists have failed to ascertain, 

 with absolute accuracy, the amount of solid matter in the serum of 1000 parts of 

 blood." The error, 1 in the present state of our knowledge, is unavoidable. 



The clot which remains after the removal of the serum, is next cut into thin 

 slices, and inclosed in a muslin bag, and carefully washed under a stream of water 

 until the fibrin remains in the bag free from serum and blood-corpuscles, and 

 becomes almost colorless. 



Another method of obtaining the fibrin, is to receive into a small glass botrle 

 (capable of containing from two to four fiuidounces) a portion of blood, and then 

 dropping in some dozen small strips of lead, and closing with the stopper, agitate 

 and shake until the fibrin coagulates around the lead strips. Two strong objec- 

 tions lie against the employment of this method in investigations upon cold- 

 blooded animals. 1st. Their blood, in most cases, cannot be obtained in sufficient 

 quantities. 2d. The fibrin, in most individuals, is so soft, that it will not coagulate 

 around the lead strips. Neither of these methods is strictly correct. A portion of 

 the fibrin is necessarily lost during the process of washing, and that which remains 

 always contains colorless blood-cells and remains of colored cells. 



The fibrin thus obtained is placed in a small evaporating dish, and dried upon 

 the chloride of calcium bath, until it ceases to lose weight. If we wish still greater 

 accuracy, the fatty and extractive matter may be removed by alcohol and ether, 

 and, after complete drying, its weight is ascertained, and it is finally incinerated 

 and the weight of the ash deducted. The proportion of fibrin in 1000 parts of 

 blood may be determined by a simple proportion. 



The amount of albumen and extractive matters in 1000 parts of blood may be 

 determined by subtracting the saline matter of the serum of 1000 parts of blood, 

 from the solid residue of the same. 



From the third portion of blood (/), we have determined the following con- 

 stituents: — 



1 Several physiological chemists have attempted, without success, to avoid this source of error, by 

 determining absolutely the amount of blood-corpuscles. 



