196 Proceedings of Royal Society of Edinburgh. [sess. 
one cannot get the two bands to give place to the one band, even 
after three hours — a most striking additional proof of the great 
relative difference in deoxidising energy possessed, on the one 
hand, by amphibian (cold-blooded) living tissue, and on the other, 
by mammalian (warm-blooded) tissue. 
It demonstrates the very much more active deoxidative kata- 
bolism of the rabbit’s tissues compared with the frog’s. Since 
making these observations, I have seen Yeo’s paper (8) upon the 
respiration of cardiac muscle, in which he finds, in the beating frog- 
heart, fresh mammalian blood perfused is reduced in from 30'-55', 
showing, precisely as one would expect, the much more energetic 
katabolism in a frog’s heart than in a frog’s leg. 
IX . — The Guiac and Peroxide of Hydrogen reaction with 
Hcemoglobin Derivatives. 
The following pigments yield the blue colour of this test : — 
Oxyhaemoglobin, even in very dilute solution, neutral and 
alkaline metdisemoglobin, acid haematin, alkali haematin, and 
CO-HbO. 
The following do not yield the blue colour : — 
Eeduced HbO, haemochromogen, acid haematoporphyrin, the red 
ally of uro-haematoporphyrin. This latter list is interesting in that 
they are all more or less reduction-products of Hb0 2 . 
Using this test to discover the minimal quantity of Hb0 2 which 
it could detect, I find that it still yields a blue with so small an 
amount as 5 minims of blood, diffused through 750 c.c. of water; 
this represents ’04 per cent, of blood, which corresponds to *0056 
per cent, of Hb0 2 in the water. 
With the spectroscope I noticed that on diluting down one 
could detect *625 c.c. in 1100 c.c. of water, and *3125 c.c. in 
1300 c.c. of water, although at this point the band could only 
be viewed obliquely: at *3125 c.c. in 1500 of water the f band 
had vanished, i.e., the spectrum had just become atypical. This 
represents *02 per cent, of blood, which is equivalent to *0028 per 
cent, of Hb0 2 in the urine ; this figure is very nearly Preyer’s for 
the minimum visibility of Hb0 2 , viz., *003 per cent. Since the 
spectroscope can detect - 0028 per cent, of Hb0 2 as compared with 
