190 
Proceedings of Royal Society of Edinburgh. [sess„. 
III . — The Spectroscopy of Met-Hcemoglobin. 
This pigment appears under various chemical conditions ; thus,., 
exposure to the air of a thin layer of dilute blood, or merely corking 
dilute blood in a large bottle, is sufficient to form some. These- 
solutions first become acid and show this pigment before there is 
any alkalinity with putrefaction and reduction of Hb0 2 to HbO. 
But, as is very well known, this pigment is formed when a 
nitrite, even amyl nitrite, or potass, permanganate, or KC10 3s , 
or formyl aldehyde, or a dilute acid (3), acts upon the blood. 
The last mentioned is probably the method by which met- 
haemoglobin appears in the urine, being produced in it by the 
weak acid, for it seems certain that one never finds acid or alkali 
hsematin in urine, but only Hb0 2 , or HbO, or met-haemoglobin. 
I kept Hb0 2 in contact with both alkaline and acid urines for 
periods varying from thirty-six hours to two months, and only 
found alkaline haematin in alkaline urine after the latter period. 
I never found acid haematin in any urine whatever. Only strong 
acids can form it. In a clinical case of “blood in the urine” 
(carcinoma of kidney), I obtained a spectrum which could only be^ 
interpreted by recognising that we had both Hb0 2 and acid met- 
haemoglobin simultaneously present. 
It was not acid-haematin, for — (1) Am 2 S reduced the whole to 
HbO ; and (2) dilution with half its volume of water caused the 
band in the red to disappear, which is precisely how that band of 
met-haemoglobin behaves — it tends to disappear in dilute solutions 
with more celerity than any other band in the red. Thus there is 
no doubt this was not a case of met-haemoglobinuria, but merely of 
haematuria in which some met-haemoglobin was formed by the weak 
acid of the urine acting on the blood, either in the bladder or after 
being passed. 
When met-haemoglobin is reduced by Am 2 S, it passes through 
the stage of Hb0 2 before becoming HbO : this has given rise to 
the idea that it is u hyperoxygenated Hb0 2 ” ; the oxygen is, how- 
ever, rather more firmly fixed in it than in Hb0 2 . When HbO,. 
so produced, is re-oxygenated, only Hb0 2 and not met-haemoglobin. 
is obtained; thus there is no pigment “ reduced met-haemoglobin” 
per se, in the same sense that there is a reduced alkali haematim 
