200 PHYSIOLOGY. 



of pathology ; but I allege that it has been for the most part 

 hypothetical ; and has hardly, so far as I know, in any case 

 been ascertained as a fact. I am disposed to maintain, that the 

 supposition is for the most part improbable. The functions of 

 the economy, depending upon the constant motion of fluids 

 through many narrow canals, require that those fluids should 

 have a very great fluidity ; and accordingly Nature has, for 

 this purpose, provided, that a pure water should always make a 

 very great part of the animal fluids. It is also certain, that 

 those parts whose particles might be disposed to unite together, 

 and to form impermeable masses, are for the most part held in 

 a state of solution, and in a very fluid state ; or if there are cer- 

 tain parts which are only in a diffused state, these are in very 

 small proportion to the entirely fluid parts ; and while the heat 

 and mobility of the whole continue, the cohesive matters are 

 kept in a very minutely divided state, and diffused amongst the 

 more fluid parts ; and there is not any evidence of their sepa- 

 ration from those fluids but in consequence of stagnation. 

 There is therefore little foundation for the supposition of a pre- 

 ternatural spissitude prevailing in the mass of blood, or of its 

 proving commonly the cause of disease." M. M. 



CCLX. We would next put the question By what means 

 the parts of this heterogeneous mass are kept so equably diffused 

 among one another, and the fluidity of the whole so constantly 

 preserved? This we suppose to be done chiefly by motion 

 and heat, and by the parts disposed to concrete being kept from 

 the contact of any matters to which they might adhere more 

 firmly than they do to the other parts of the blood. The dif- 

 fused parts we suppose to be present only in those vessels in 

 which a considerable degree of agitation is constantly kept up ; 

 and we suppose also that the heat always here present both di- 

 minishes the cohesion of the gluten, and increases the solvent 

 power of the serosity. Experiments made with neutral salts 

 seem to confirm the latter ; and it is also probable that the same 

 solvent power may be increased by a quantity of air that is con- 

 stantly intermixed with the mass of blood while it remains in the 

 vessels, and is under a constant agitation. It is supposed that 

 an attention to these several circumstances will explain most of 

 the cases of spontaneous separation that occur either in the liv- 



