158 THE BLOOD. 



than 50,000 times greater than the power of gravity, is constantly 

 generated (under the galvanic influence, for example) by the 

 alloy of mercury with a millionth part of its weight of sodium. 

 Dr. Prout regards these incidental particles as in a state of mutual 

 repulsion, because, instead of being equally diffused as they are, 

 they would otherwise be collected into a mass or crystal. d 



I may mention, that Dr. Prout says perhaps it may be stated 

 as a general law, that no substance, entering into the com- 

 position of a living plant or animal, is so pure as to be capable of 

 assuming a regularly crystallised form. Instead, therefore, of 

 being defined by straight lines and angles, all solid organised 

 substances are more or less rounded, and their intimate structure 

 is any thing but crystallised. The composition of organised fluids 

 is equally heterogeneous ; and, though the basis of nearly every 

 one of such fluids is water, many of them contain a variety of 

 other matters. 



M. Raspail remarks further, that the constituents of organic 

 solids or fluids are not combined in definite proportions, like those 

 of inanimate bodies, but are ever variable, so that the varieties of 

 each compound are infinite. e 



d Bridgewater Treatise, p. 425. sq. 



e 1. c. p. 78. sq. 



" The idea of succession and developement leads to the conclusion, that, if the 

 products are examined at a certain period, they will be found chemically more or 

 less heterogeneous, and more or less mixed. In some, the combined water and 

 carbon are not yet combined with a base, or at the utmost are mixed with one ; 

 then we have gum. In others, the carbon is mixed with hydrogen only, or 

 at the utmost with a small quantity of water : that this may assume the charac- 

 ters of a substance fit for organisation, it must obtain sufficient oxygen aspired by 

 the cellular apparatus, to transform all the hydrogen into water ; till then the 

 compound was an oil, or resin. Finally, the carbonic acid absorbed, instead of 

 uniting with a quantity of hydrogen sufficient to convert the oxygen of the acid 

 into water, may unite with a fresh quantity of water or other substances, even 

 with a quantity of salts insufficient to neutralise them, and then, becoming an 

 acid of a new form, it will serve as a brute unorganised body for the elabo- 

 ration or the decomposition of the salts which are necessary for the developement 

 of the tissues." 



Most cold-blooded animals, as fishes and the amphibia, have a much smaller 

 proportion of blood and fewer blood-vessels than those with warm blood, though 

 a much greater number of colourless vessels arising from the arteries. In an 

 experiment which Blumenbach made on this subject, he " obtained from twenty- 



