200 THE BLOOD. 



The fats of the blood are contained in a, from which they 

 are extracted by repeatedly treating it with ether and evapo- 

 rating the ethereal extract. The residue is washed into a 

 small platinum capsule for incineration. 



b is incinerated in the capsule in which it was weighed ; c, 

 with the filter in which it is contained, is incinerated in another 

 capsule. The ash of a and b represents the soluble salts of 

 the blood, viz., the chloride of sodium (five-sixths of the 

 whole), phosphate, sulphate, and carbonate of soda ; chloride 

 and sulphate of potash. The ash of c consists of phosphates 

 of lime and magnesia. 1 



2. A second quantity of twenty-five centimetres is used for 

 the determination of the fibrin. For this purpose a small 

 beaker is used, over the top of which a vulcanized India-rubber 

 cap with a single neck (see Fig. 196) can be drawn without 

 difficulty. Through the neck or tubulature, a rod of whale- 

 bone, which, at its lower end, widens out into a blade, is 

 grasped by the tubuliiture. The blood is received into the 

 beaker, covered at once with the cap, and immediately agitated 

 very briskly with the blade of the whalebone, the purpose of 

 the whole arrangement being to prevent loss of weight by 

 evaporation during the process. As soon as coagulation is 

 complete, the beaker and its contents are weighed. The 

 weight, minus that of the beaker, its cover and the oar, is that 

 of the quantity of blood usecl. The cover is then removed 

 and the beaker filled with water, to which a trace of chloride 

 of sodium has been added. After agitation and subsidence 

 the clear liquid is poured off, and the fibrin again treated with 

 as much more water with a trace of salt. The fibrin is then 

 collected on a weighed filter, and washed with distilled water 



1 In incinerating, it is of importance that the capsule or crucible 

 should be large enough to hold four or five limes as much material as is 

 used. Platinum vessels are preferable. If the substance contains much 

 organic matter, and at the same time much soluble salts, e. g., chlorides, 

 it is necessary to perform the operation in two stages, i. e., first to car- 

 boni/.c the substance, then extract the ash with boiling water, collect 

 the insoluble part o'n a filter free from ash or containing a known 

 weight of ash. The filter, after careful washing, must be dried at 

 110 C., and gradually heated to whiteness until the carbon is entirely 

 destroyed. Almost the whole of the soluble salts arc contained in the 

 extracts. Thus the decomposition of the alkaline carbonates and 

 chlorides, which occurs at a higher temperature, is avoided. In incine- 

 ration of the total solids of the blood this interruption of the process is 

 desirable, if for no other reason, on account of the extreme difficulty of 

 getting rid of the carbon in presence of so great a quantity of alkaline 

 salts. If, however, the method described in the text is followed, these, 

 difliculties are got rid of in another way. For, on the one hand, the 

 watery and alcoholic extracts contain very little organic matter ; on 

 the other, the insoluble residue (c) is free from alkaline salts. In both 

 cases, therefore, the incineration can be proceeded with continuously. 



