180 Prof. Draper on the Cause of the 



fibrine from the vegetable world. During the incubation of 

 an egg we see this substance arising from albumen, and the 

 analogy is probably continued in higher forms of existence. 

 Neither is it by any means certain that fibrine exists in a state 

 of solution in the blood. But, as we shall presently see, the 

 probabilities are that it coagulates as it is produced by the 

 metamorphosis of the blood, that metamorphosis being ori- 

 ginally due to the act of respiration. Under an accelerated 

 respiration, the discs oxidize with corresponding rapidity and 

 the amount of fibrine increases; but if the supply of oxygen 

 be limited, there is a restraint on the change of the discs, and 

 the amount of fibrine declines. 



The ultimate products of these metamorphoses include of 

 course all the results of the intervening stages, and those ul- 

 timate products are chiefly water, ammonia and carbonic acid. 

 We are justified therefore in these physiological discussions in 

 looking at the whole process as one of oxidation, and neglect- 

 ing intermediate metamorphoses we regard only the final ac- 

 tion, and that action is the transmutation of oxygen into car- 

 bonic acid, of hydrogen into water, of nitrogen into ammonia. 



Explanation of the General Physical Principle. — If, in a 

 vessel containing some water, a tube of small diameter be 

 placed, the water immediately rises to a certain point in the 

 tube and remains suspended. 



Let the tube be now broken off below that point, and re- 

 placed in the cup of water; the liquid rises as before, but 

 though it reaches the broken extremity it does not overflow. 

 A capillary tube may raise water to its highest termination, 

 but a continuous current cannot take place through it. 



Now, suppose a rapid evaporation of the liquid to ensue 

 from the broken extremity of the tube, as fast as the removal 

 of one portion is accomplished others will rise through the 

 tube, and in the course of time the vessel will be emptied. 

 By evaporation from the upper extremity a continuous cur- 

 rent is established ; a spirit-lamp, with its cap removed, is an 

 example of this fact. 



Or, if the liquid which has risen to the upper end of the 

 tube be of a combustible nature, oil for example, and be there 

 set on fire, as the process of combustion goes on a current 

 will be established in the tube, as in a common oil-lamp in 

 the act of burning. 



The principle which I wish to draw from these well-known 

 facts is, that though ordinary capillary attraction cannot de- 

 termine a continuous flow of a liquid through a tube, there 

 are very many causes which may tend to produce that re- 

 sult. 



