314 Appendix I. On methods 



and the end of the delivery pipette on the bottom, the blood can then drain into the 

 cup for it before the tonometer is allowed to cool. 



In emergencies the domestic bath fitted with hot and cold water serves excellently, 

 it is large enough to accommodate the tonometer vertically as well as horizontally. 



The method of determination of the percentage saturation of the blood has already 

 been described. It is usually desirable to analyse the air in the tonometer after the 

 blood has been taken out. For this purpose the tonometer must be placed with the 

 cork downwards, the nozzle being connected to the gas analysis apparatus by a bent 

 tube (either of glass or rubber) of fine bore. The dead space is cleared of blood by 

 forcing some mercury into the tonometer, gas is then withdrawn. In calculating the 

 pressure allowance must be made for the expansion of the gas into the analysis 

 apparatus. 



APPENDIX II. ON THE AGGREGATION 

 OF HAEMOGLOBIN 



Whilst this book has been in the press some further information has been 

 acquired relating to the concentration of carbonic acid to which a dialysed solution 

 of haemoglobin is exposed to the degree of aggregation of the haemoglobin molecules. 

 It has been shown in Chapter V that alterations in the concentration of C0 2 have 

 very little effect on the value of n in the case of blood, H being the average in 

 number of molecules (each containing one atom of iron) in a clump, and having the 

 value 2'5. In the case of high concentrations of CO 2 there seemed to be some 

 evidence of a slight increase in the value of n. The most natural interpretation of 

 this was that the salts present in the blood determined the value of n and the CO., 

 the value of K in the equation 



y Kx n 



Too" 



the two effects being therefore quite different in kind. From this supposition it 

 would follow that the dissociations of dialysed haemoglobin in the presence of in- 

 creasing quantities of C0 2 would be a series of rectangular hyperbolae presenting the 

 general appearance shown in Fig. 13 in which n in each case was unity and K 

 diminished as the C0 2 pressure increased. 



Experiment shows that this conception is quite at variance with the facts. The 

 following are the values of K and n for the dissociation curves of dialysed haemo- 

 globin in the presence of the stated pressures of C0 2 at 40 C. 



CO., pressure n K 



mm. 1 'HI 



8 ,, 1-78 -0062 



33 ,, 2-5 '00049 



67 2-7 -000192 



