Physiological Researches on Life and Death

by Xavier Bichat

2dly, Examine two men, the one with a rosy coloured skin and large breast, announcing vigour of lungs, the other with a pale and sallow countenance, and narrow chest: in these the vigour of the chemical combinations which are made in the lungs, should certainly be very different.

3dly, The greater number of gangrenes in old men, begin with a lividity in the part, a lividity which is evidently the index of the absence or diminution of the arterial blood in the part.

4thly, The redness of the branchiæ of fish is always the sign by which their vigour may be recognised.

5thly, The redder the granulations of wounds, the more healthy is their nature; the paler or browner they are, the less has the part a tendency to cicatrise.

6thly, The lively colour of the face, and the ardent eye, coincide with the energy of the cerebral actions in certain fevers.

7thly, The more developed the pulmonary system of animals, the more active are the chemical processes of the lungs, and the more developed and perfect the general life of their different organs.

8thly, Youth, which is the age of vigour, is that also when the red blood predominates in the system. The arteries of old people are smaller, the veins larger than those of the young. It is a fact universally known, that at the two extremities of life the proportions of the two vascular systems are inverted.

I am ignorant of the manner in which the red blood excites and keeps up the life of the parts. Perhaps the principles by which it is coloured become combined with the different organs to which it is distributed. In fact there is a considerable difference between the phenomena of the general and those of the capillary system.

In the first, the blood in changing its colour, leaves behind it the principles which made it red; in the second, the elements to which its blackness is owing, are rejected by respiration and exhalation. Now, this union of the colouring principles of the arterial blood, may probably constitute a material part of the excitement which is necessary to the action of the organs.—If such be the case, the black blood as it does not contain the materials of such union, cannot act as an exciting cause. This idea, however, I offer only as a probability, and am by no means prepared to defend it as a truth; it may be ranked on a par with that of the sedative action, which I have said may be excited by the black blood on the different parts—for, however probable an opinion may appear, there should be no real importance attached to it as an opinion only.