376 DISCOVERY REPORTS 



burette agreed, after correction, with the theoretical values to within 5 per cent. Each 

 sample was re-evacuated after the gases had been measured to ensure that extraction 

 was complete. 



The various body fluids will now be dealt with in detail in the following order : urine, 

 allantoic fluid, liquor folliculi, maternal and foetal blood. The gas contents of blubber 

 and connective tissue will also be considered. 



URINE 

 Hill records the accuracy with which the pressure conditions in the lungs of an animal 

 were reflected by the nitrogen content of the urine ; advantage was taken of this to find 

 out the degree of supersaturation of urine caused by various pressures in the lungs 

 by drawing the fluid under cover and analysing the dissolved gases. Since the bladder 

 of a Blue whale is nearly always full after death with the walls in a state of tight contrac- 

 tion, against which the sphincters seem able to retain the urine, it was thought that 

 samples of urine from freshly killed whales would be valuable in giving some indication 

 of the gaseous conditions obtaining during the last half hour or so of the whale's life. 

 The bladder is extremely tough and thick, and since there was never gas in the bladder 

 except in one case it is fairly certain that if supersaturation of the urine was found it 

 indicated at least the same amount of supersaturation before death. Supersaturation 

 could not have occurred after death. 



The procedure was to puncture the bladder with a sharp knife and quickly immerse 

 a large test-tube in the urine. The tube was immediately closed with a rubber bung 

 while still submerged and promptly placed in a pot of ice-cold water. The last move 

 prevented any tendency to effervescence, in the event of supersaturation, by increasing 

 the solubility of gases in general through lowering the temperature. The tube was then 

 conveyed to the laboratory, and some of the contents drawn from the bottom under 

 paraffin were pipetted into the receiving cup of the gas burette. 0-05 A^ lactic acid, 

 previously evacuated, was used in the liberation of carbon dioxide. 



Several estimations were performed on the same sample of urine. The specific gravity 

 of some specimens was taken, the sodium chloride content by Volhard's method, total 

 carbon dioxide content, and carbon dioxide combined as carbonate and bicarbonate. 

 The dissolved and combined carbon dioxides were differentiated in this way. The total 

 carbon dioxide in the urine was liberated in the burette with the aid of lactic acid. 

 Another portion of the same sample was thoroughly aerated and treated in the burette 

 similarly. Aeration was repeated until a constant minimum carbon dioxide content was 

 found. The difference between the first and second estimations of urine was taken to 

 be the volume of dissolved gas. Professor Krogh has stated that this method of dis- 

 criminating between free and combined carbon dioxide is approximately valid only 

 when the fluid is fairly acid (pH < 5). It was found, however, that the volume of 

 carbon dioxide which was removed by aeration was exactly equal to the volume which 

 could be liberated by evacuation without reagents. In other words the method was 

 approximately accurate for the measurement of dissolved carbon dioxide. 



