ANIMAL FLUIDS AND TISSUES. 431 



Weigh a few grammes of the dried animal matter and digest it in a stop- 

 pered flask with about 10 parts of ether for an hour ; filter, and repeat the 

 operation once or twice ; allow the ether to evaporate in a small dish, previ- 

 ously weighed ; the residue left consists chiefly of fats, which may be recognized 

 by their physical properties. 



Digest the animal matter left from previous treatment twice with hot alcohol 

 and twice with boiling water ; evaporate the alcoholic and aqueous solutions 

 separately ; they contain the so-called extractives and soluble salts. 



Dry the exhausted animal matter completely as before and weigh it ; it con- 

 sists chiefly of insoluble salts and albuminous substances. Ignite and burn 

 as stated above. The loss represents mainly albuminoids. Notice the differ- 

 ence between the percentage of inorganic matter left now and in the deter- 

 mination made before ; this difference represents the soluble inorganic com- 

 pounds. 



Blood. Two kinds of blood are distinguished, the arterial or oxi- 

 dized and the venous or deoxidized blood. Arterial blood as it is 

 present in the system, or immediately after it has been drawn from 

 the body, is a red liquid of an alkaline reaction and a specific gravity 

 of about 1055. Upon examination under the microscope, blood is 

 seen to consist of a colorless fluid, called plasma or serum, in which 

 float small globules or corpuscles which make up about 40 per cent, 

 of the whole volume of blood. These corpuscles are of three varie- 

 ties, viz. : red and white corpuscles, and blood plates. The red cor- 

 puscles, which give to the blood its red color, are biconcave discs, 

 about 33*00 of an inch in diameter; the white corpuscles are simple 

 cells, and somewhat larger than the red corpuscles ; they are present 

 in the proportion of about 1 to 350 of red. More recently have been 

 discovered "blood plates," pale, colorless, oval, round or lenticular 

 discs which vary in size. 



The composition of normal human blood is about as follows : 



Water . . . 79.50 per cent. 



Serum-albumin 7.34 " 



Fibrin 0.21 " 



Haemoglobin 11.64 " 



Fatty matters 0.18 " 



Extractives 0.32 " 



Ash 0.81 



AYet red blood-corpuscles contain of water 54.63 per cent., haemo- 

 globin 41.1 per cent., other proteids 3.9 per cent., fats (chiefly chole- 

 sterin and lecithin) 0.37 per cent. The quantity of water in corpus- 

 cles varies widely, and most likely ranges in healthy blood from 76 

 to 80 per cent. Dried corpuscles contain of haemoglobin about 90 

 per cent. 



