If one were to neglect John Hunter's dictum, "Don't think, but try," he would be led into all sorts of misconceptions regarding the changes in the quality of the blood. As might be expected, there is a slight reduction in the total quantity due to the loss of water, but there appears to be little alteration in the character of the blood, excepting a relative increase of the other constituents on account of its slightly inspissated condition. Observers appear to differ somewhat in their opinion as to the actual changes which occur. Von Noorden declares that the leucocytes are slightly diminished in number and the alkalinity unaltered. The fatty content is increased because the tissue fat is being consumed and is conveyed to the fasting organs by means of the circulating blood. Sugar is always present in small quantities, because glycogen is constantly being formed, in the later stages of course from tissue protein, and the glucose in the circulation is the visible expression of its transportation from the liver to the muscles. The quantity of globulin is slightly increased in the blood plasma, no doubt owing to myosinogen being transferred from the muscles to become serum globulin.

On the other hand, other experimenters state that there is. a progressive average fall in the number of erythrocytes, and an accompanying diminution in the percentage of haemoglobin. There is also a relative progressive fall in the percentage of leucocytes, but the various types appear to maintain their relative proportion to each other. Most observers agree that there is a relative leucocytosis which would explain the high percentage of polymorphonuclear leucocytes and large lymphocytes and the relative low percentage of small lymphocytes.

The body temperature follows the normal variations, the average difference being '5° C. while fasting, instead of 1° C. when not. At the termination of Succi's forty days' fast at the Royal Aquarium his temperature was 97.4° F. On account of the combustion of the fat and tissue protein the temperature is well maintained, rarely falling more than 1° F. until the end of a long fast, when it gradually sinks, and a few days before death rapidly falls, because the supplies are exhausted and the heat-regulating functions destroyed. All fasting subjects complain bitterly of the cold, and if they can only be provided with a sufficiency of external warmth they will survive for a much longer period.

In all cases under the care of skilled observers the pulse rate, volume, and strength notably decreased, as might have been expected, but upon the slightest indulgence in exercise the pulse rate was accelerated to a point much higher than the normal. Zuntz, in his observations in Cetti's case, remarks, "One can assume that during fasting, in consequence of the ease with which the heart is fatigued, exhaustion will readily make an end of the possibility of doing work before any accessory muscles can be called into play."

Despite this statement, however, and although the loss of strength is usually progressive, it is not always so. On the twelfth day of Succi's thirty days' fast he rode for an hour and forty minutes on horseback, walked some distance in the evening, engaged in a racing contest for eight minutes against three students, and finally had a bout of fencing, taking in all 19,900 steps during the day. Again, on the twenty-third day he visited the theatre and indulged in fencing bouts with swords, the number of his steps on this occasion amounting to 7,000. All this work, however, was insufficient to increase the excretion of urinary nitrogen beyond the usual amount, but was accomplished by an increased metabolism of fat.

The blood-pressure is always reduced.