70 THE BLOOD. 



Viscidity is another property of the blood equally im- 

 portant with its coagulation ; for the same authority asserts 

 that the circulation is due to this property, and if lost or 

 taken away ; the blood is arrested in its course. 



He states the remarkable fact that if we attempt to in- 

 troduce water into a tube of extremely small diameter, it 

 will not enter, no matter what force be employed; but sim-- 

 ply add a certain quantity of gum, gelatine or any mucila- 

 ginous substance, and the attempt becomes "immediately 

 successful." 



The blood, however, on the other hand, can be too viscid, 

 and by adhering to the sides of the vessels mechanically 

 obstruct the circulation. 



The force with which the blood presses against the ar- 

 teries, by the experiments of M. Poiseuille, is nearly the 

 same in every part of the body. 



The rapidity of the blood is estimated at 149.2 feet per 

 minute; going the whole round of the circulation in about 

 three minutes; requiring in this time about 240 beats of 

 the heart, each beat sending forward 2 oz. of blood, and in 

 one hour 20 times the whole weight of blood in the body. 



There are other physical properties of the blood, as elas- 

 ticity, density, cohesion, &c., all of which modify its char- 

 acter, and through it, to a greater or less extent, the differ- 

 ent organs. 



Now all the properties just enumerated owe their exist- 

 ence and value to the unalterable relations which nature 

 has established between the blood on the one hand, and 

 the external bodies of food, atmospheric air, water and 

 temperature on the other which relations, if we violate, 

 will be vindicated by a proportionate alteration or destruc- 

 tion of the physical properties of the blood, and a conse- 

 quent proportionate impairment of the health of the body. 



The chemical properties of the blood are thus given by 

 M. Lecanu, whose analysis is regarded as among the most 

 .accurate. He makes 25 distinct substances, to wit: 



