568 SCIENCE PROGRESS 



(}) Mammals. — The fluids of physiological importance in 

 mammals have been investigated fairly thoroughly ; besides 

 the blood, those most studied have been the milk and the urine. 

 As a whole the freezing-points of the blood of the group lie 

 between —0*55° and — o'6o° C, and when one considers the 

 vast amount of anabolic and katabolic changes ceaselessly in 

 progress in the body, such constancy as is met with in each 

 particular species is most remarkable. In fact it is no less 

 wonderful than is the constancy of temperature, the wonder of 

 which is forced upon any biologist who has to construct a 

 thermostat. 



In man, for example, the normal freezing-point of blood is 

 — o*56°. It may vary o"oi° perhaps in health. After severe 

 haemorrhage, when the body salts have been lost in quantity, 

 it has within the writer's experience fallen to — 0*53°, and even 

 in one case to —0*49°. This is probably the lowest value re- 

 corded. In kidney disease, on the other hand, the depression of 

 freezing-point may be greater than the normal. If it is neces- 

 sary to remove a diseased kidney it is prudent to ascertain first 

 of all that the blood is normal ; for it has been found that if the 

 blood freezes at — o*6o° or lower when both kidneys are in the 

 body, the removal of one of them is always fatal . For if both 

 together fail to preserve a normal molecular concentration in 

 the blood, the removal of one, even if seriously diseased, results 

 in the production of such accumulation of katabolic toxins as to 

 result in death. Among a limited number of samples of blood 

 from kidney patients submitted to the writer it was found that 

 two exceeded the limit — o'6o° laid down by von Koranyi, 

 and by Caspar and Richter. Removal of the kidney would 

 therefore in these cases have been worse than useless. By 

 examining the freezing-point of the urine collected from each 

 ureter separately it is also possible to get a quantitative measure 

 of the functional activity of the two kidneys. In health the 

 values found lie between — o'9 6 and — 2*1°. With diseased 

 organs, however, it is usual to find lower values, — o m 6 or there- 

 abouts. 



The freezing-point of milk is also, like that of blood, very 

 constant. Winter and Nernst were among the first of many to 

 study it. That of the cow lies at —0*55°, a slightly lower 

 numerical value than that of its blood. Variations exceeding 

 cro2° are very rare, and seeing that the milk is a secretion from 



