68 THE NEW PHYSIOLOGY. 



by his observations that in prolonged starvation there is 

 still sugar in the blood, and that even when great excess 

 of sugar is introduced into the body the percentage in 

 the blood remains very steady, as excess is taken up by 

 the liver and other organs, or excreted by the kidneys. 

 Voit's observations on the relative constancy of the 

 sodium chloride in the blood, and the manner in which 

 the kidneys regulate this percentage, are of a similar 

 character. If food freed from chloride is administered, 

 the elimination of chloride by the urine diminishes to 

 almost nothing, though the high percentage of chloride 

 in the blood-plasma remains about the same. As Voit 

 also showed, the blood during prolonged starvation 

 retains its normal composition, and its volume remains 

 proportional to body weight, while other tissues (e.g. t 

 muscle) are disproportionately reduced. 



Dr Priestley and I have recently investigated the excre- 

 tion of water by the kidneys. By simply drinking large 

 quantities of water one can produce an enormous in- 

 crease in the secretion of urine, and this urine is almost 

 pure water. What we wished to observe was the degree 

 of watering down of the blood which was necessary to 

 produce the huge increase hi excretion of water. We did 

 not doubt that the watering down would be very small, 

 but when we attempted to measure the dilution by deter- 

 mining the percentage of haemoglobin, we found that there 

 was no dilution at all, though the method used was one 

 of extreme accuracy. When, however, the plan of 

 measuring the electrical conductivity of the serum was 

 adopted, a slight, but quite distinct, diminution in the 

 conductivity could be detected during, and ending with, 

 the diuresis. This showed that there was a slight diminu- 



