172 CIRCULATING FLUIDS: 



and renewed until the fibrin is found to be colourless, which is 

 usually the case in from 1 8 to 24 hours. It is almost needless 

 to mention that none of the flocculi of fibrin must be allowed 

 to escape when we pour off the water. The decolorized fibrin 

 is driedj cautiously broken up, pulverized in an evaporating 

 basin, and then submitted to a temperature of 230° until it 

 ceases to lose weight, i It is then weighed. It is again finely 

 triturated, placed in a flask and heated, first Avith anhydrous 

 alcohol, and then with ether, for the purpose of extracting the 

 whole of the fat. The ether and alcohol must be evaporated in 

 the water -bath, and the weight of the fat estimated. The quan- 

 tity of fibrin and of fat associated with it must then be cal- 

 culated in regard to the whole quantity of the blood. 



c. A quantity varying from 30 to 50 grains of defibrinated 

 blood must be accurately weighed in a small basin, and cau- 

 tiously heated over the flame of a spii'it-lamp. This portion 

 must then be triturated, submitted to the action of the water- 

 bath, pvilverized as completely as possible, and the heat conti- 

 nued until it ceases to lose weight. Lastly, it must be heated 

 in a chloride of zinc bath to 230°. The loss of weight indicates 

 the quantity of water. 



d. An optional quantity (say from 400 to GOO grains) of defi- 

 brinated blood, must be boiled over the flame of a spirit-lamp, in 

 order to coagulate the whole of the albumen, and subsequently 

 placed on the water-bath for the purpose of removing all mois- 

 ture. As soon as the blood has become sufficiently dry to ad- 

 mit of being partially broken up, it must be carefully triturated 

 in a mortar, and then again j)laced on the water-bath. All the 

 tough coriaceous portions, which are not easily pulverizable, 

 must be carefully removed : by further drying they become ge- 

 latinous, tough, and ultimately brittle. The powdered blood 

 ought, however, if the previous steps have been properly exe- 



' I may observe that, in my analyses of blood, I always use small porcelain basins, 

 weighing from 200 to 300 grains, and that I pulverize dried substances in the basins 

 themselves with a small pestle. As these substances, when thoroughly dry and M^arm, 

 are apt to exhibit a strong electrical repulsion of their particles, it is advisable to 

 place the basin on a sheet of glazed paper, by which precaution any portion that may 

 escape from it can be easily replaced. Any particles adhering to the fingers or to 

 the pestle may be swept off with a soft feather. The most scrupulous exactness and 

 accuracy is requisite in these iuvestigations. 



