It wastes in the disease known as " myxoedema," and the above product gathers in the tissues, in that disease, to such an extent as to give rise to what has been termed a " solid oedema."
We find at this early stage oedema of the part.
Thus differences in osmotic pressure may be much more powerful in producing oedema than mere differences in blood pressure.
It is invariably the result of some cause acting generally, such as renal disease, valvular defect of the heart, or an impoverished state of the blood; while a mere oedema is usually dependent upon some local obstruction to the return of blood or lymph, or of both, the presence of parasites within the tissue, such as the filaria sanguinis hominis or trichina spiralis, or the poisonous bites of insects.
Welch produced oedema of the lungs experimentally by increasing the pressure in the pulmonary vessels by ligature of the aorta and its branches, but this raised the blood pressure only about one-tenth of an atmosphere, while in some of Loeb's experiments the osmotic pressure, due to retained metabolic products, was equal to over thirty atmospheres.