OF THE BLOOD. 7 



vessel of larger area, that they again resume their glo- 

 bular shape.* This, although I would by no means 

 deny it, I cannot conceive to occur during the tranquil 

 and healthy motion of the blood, but should refer it to 

 a spasm of the small vessels. 



Their globular figure can be seen in a living animal 

 only, or in blood very recently drawn: for they are 

 soon unobservable, becoming a shapeless mass which 

 resembles serum in every circumstance excepting 

 colour. 



13. Their colour is red, and from it is derived the 

 colour of the blood. In intensity it varies infinitely; 

 paler in animals which have been poorly nourished or 

 have suffered from haemorrhage; more florid, when 

 oxygenisedf (rendered arterial, to use the common 

 phrase) by exposure either to atmospheric air, or, more 

 especially, to oxygen; darker when carbonised, (in 

 common language, rendered venous) by exposure to 

 carbonic acid gas, or to hydrogen. The redness is 



* G. Chr. Reichel, De sanguine ejusque motu Experimenta. Lips. 1767. 4to. 

 p. 27. fig. 3. g. g. 



f Unwilling as I am to follow the example of those, who, especially in modern 

 times, delight in changing scientific terms, I cannot but think that the words 

 oxygenized and carbonised may be advantageously substituted for arterial and 

 venous : because arterial blood is contained in some vessels called veins, v. C. 

 the pulmonary and umbilical ; while, on the other hand, venous blood is con- 

 tained in the pulmonary and umbilical arteries. In the same manner, the veins 

 of the chorion in the incubated egg contain arterial, the arteries, venous, 

 blood ; to use these expressions in their common acceptation. 



J Consult among others whom we shall recommend in the chapter on respi- 

 ration, Chr. Girtanner, Journal de Physique. August. 1790. 



Fourcroy, Annales de Chimie. t. rij. 



Hassenfratz, ibidem, t. ix. 



J. Ferd. H. Autenreith, Experimenta et observata de sanguine pramcrtim 

 venoso. Stuttg. 1792. 4to. 



