DR. C. A. MACMUNN ON MYOHA3MATIN AND THE HISTOHiEMATINS. 279 
matin. To be quite certain as to the exact spectra of the histohsematins in man, 
injection of the blood-vessels with salt solution would be required, and until this has 
been done I do not feel warranted in drawing conclusions from other observations 
which I have made on the human organs. In man, however, the presence of myohse- 
matin has been detected, as will be described further on, as well as its occurrence in 
the other Mammals referred to above. 
In nervous tissues* I have not yet found a liistohsematin, either in invertebrates or 
vertebrates. 
In no animal have I succeeded as yet in isolating the histohsematins. In them the 
coloured constituent occurs united to a proteid in all probability, and hence the 
difficulty attending attempts at isolation. Bisulphide of carbon, chloroform, alcohol, 
ether, benzol, petroleum, hot and cold water, alkaline water, acidulated water, and 
other solvents have been tried in vain. 
On the other hand, oxidation and reduction can be brought about in the solid 
organs and tissues. An interesting point bearing upon this is that the bands of the 
spectrum of the histohsematin in the stomach of the rat are invisible if the animal be 
killed during digestion, but bits of the stomach-wall plunged into a reducing agent, 
show in a short time the banded spectrum ; the reason of this is that the histohse- 
matin is charged with oxygen during digestion as denoted by its bandless condition. 
At all events, I have proved to my own satisfaction that the banded condition belongs 
to the reduced state, and the bandless to the oxidised; but it would appear from what 
I have to relate about myohsematin that this oxidation and reduction are not as 
simple as the reduction and oxidation of haemoglobin, for example, the oxygen being 
apparently more firmly fixed than in the case of oxyhsemoglobin. 
Thus, from Echinodermsf to man throughout the animal kingdom, we find in 
various tissues and organs a class of pigments whose spectra show a most remarkable 
resemblance to each other ; they are allied to hfernochromogen, the bands of which 
are sometimes closely imitated by the histohsematins. They are probably simpler in 
constitution than hsemochromogen prepared from vertebrate blood, at least they do not 
yield all its decomposition products; their bands are intensified by alkalies and enfeebled 
by acids, intensified by reducing agents, and enfeebled by oxidising agents ; they 
accordingly appear to be capable of oxidation and reduction and are therefore respira¬ 
tory. If this view be correct, and I have every reason to believe that it is, we may 
consider that the histohsematins are of use in enabling the tissues in which they occur 
to take up the oxygen from the circulating blood and hold it in the tissues, exchanging 
for it the carbon dioxide. Hence the histohsematins are concerned in the internal 
respiration of the tissues and organs of invertebrate and vertebrate animals. Why a 
* The occurrence of haemoglobin in the ventral chain of ganglia of Aphrodite (Lankester) is worthy 
of notice. 
f The pigments of Actinice which replace (in them) the histohaematins have been described in my paper 
on the “ Chromatology of Actiniae,” Phil, Trans., vol. 176, p. 641. 
