And hence those fevers, whose cause is from cold air of the night or morning, are more liable to observe the solar day in their periods; while those from other causes frequently observe the lunar day in their periods, their paroxysms returning near an hour later every day, as explained in Sect.  XXXVI.

IV.  Another frequent cause of the cold fits of fever is the defect of the stimulus of distention.  The whole arterial system would appear, by the experiments of Haller, to be irritable by no other stimulus, and the motions of the heart and alimentary canal are certainly in some measure dependant on the same cause.  See Sect.  XIV. 7.  Hence there can be no wonder, that the diminution of distention should frequently induce the quiescence, which constitutes the beginning of fever-fits.

Monsieur Leiutaud has judiciously mentioned the deficiency of the quantity of blood amongst the causes of diseases, which he says is frequently evident in dissections:  fevers are hence brought on by great haemorrhages, diarrhoeas, or other evacuations; or from the continued use of diet, which contains but little nourishment; or from the exhaustion occasioned by violent fatigue, or by those chronic diseases in which the digestion is much impaired; as where the stomach has been long affected with the gout or schirrus; or in the paralysis of the liver, as described in Sect.  XXX.  Hence a paroxysm of gout is liable to recur on bleeding or purging; as the torpor of some viscus, which precedes the inflammation of the foot, is thus induced by the want of the stimulus of distention.  And hence the extremities of the body, as the nose and fingers, are more liable to become cold, when we have long abstained from food; and hence the pulse is increased both in strength and velocity above the natural standard after a full meal by the stimulus of distention.

However, this stimulus of distention, like the stimulus of heat above described, though it contributes much to the due action not only of the heart, arteries, and alimentary canal, but seems necessary to the proper secretion of all the various glands; yet perhaps it is not the sole cause of any of these numerous motions:  for as the lacteals, cutaneous absorbents, and the various glands appear to be stimulated into action by the peculiar pungency of the fluids they absorb, so in the intestinal canal the pungency of the digesting aliment, or the acrimony of the faeces, seem to contribute, as well as their bulk, to promote the peristaltic motions; and in the arterial system, the momentum of the particles of the circulating blood, and their acrimony, stimulate the arteries, as well as the distention occasioned by it.  Where the pulse is small this defect of distention is present, and contributes much to produce the febris irritativa pulsu debili, or irritative fever with weak pulse, called by modern writers nervous fever, as a predisponent cause.  See Sect.  XII. 1. 4.  Might not the transfusion of blood, suppose of four ounces daily from a strong man, or other healthful animal, as a sheep or an ass, be used in the early state of nervous or putrid fevers with great prospect of success?