Observations and experiments on the colour of blood / [William Charles Wells].

  • Wells, William Charles, 1757-1817
Date:
[1797]
Catalogue details

Licence: Public Domain Mark

Credit: Observations and experiments on the colour of blood / [William Charles Wells]. Source: Wellcome Collection.

    12/18 (page 10)
    differs not only in brightness, but also in kind, from the ordi¬ nary colour of that fluid, which is a Modena red. My answer is, that there are examples, beside that to which the objection is made, of dark blood appearing florid, merely from its colouring matter being seen by means of an increased quantity of light. One is afforded by rubbing a piece of the darkest crassamentum with a proper quantity of serum; for a mixture is thus formed, in a few seconds, possessing a colour similar to that which is given to crassamentum by common air. But here we certainly do nothing more, than interpose among the red globules a number of the less dense particles of serum; which, in their present situation, act as opake matter, and con¬ sequently increase the internal reflections. A second example occurs, when we view, by transmitted light, the fine edges and angles of a piece of crassamentum in water; for, in this si¬ tuation, their colour appears to be a bright scarlet, though all the other parts of the same mass are black. These facts seem sufficient to prove, that the immediate cause I have assigned for the production of the florid appearance in blood, which has been exposed to the action of common air and neutral salts, is adequate to the effect; but I shall advance a step further, and shew how the Modena red is converted into a scarlet. Blood, as I have found by experiment, is one of those fluids which Sir Isaac Newton has observed appear yellow,* if viewed in very thin masses. When, therefore, a number of opake particles are formed in it, by the action of common air and the neutral salts, many of them must be situated imme¬ diately beneath the surface. The light reflected by these will consequently be yellow; and the whole effect of the newly-