poke. Rivy slOLOGY 
OBSERVATIONS ON THE 
GONTRACTILE “TISSUE OF THE IRIS 
[Quarterly Journal of Microscopical Science, vol. i (1853), p. 8.] 
Our knowledge of the cause of the movements of the iris was till within 
the last few years in a very unsatisfactory condition. That this organ possessed 
contractile fibres was a matter of inference, not of direct observation. In the 
third part of the last edition of Quain’s Anatomy, published in 1848, we find 
it stated (p. 915) that the radiating and circular fibres of the iris are generally 
admitted to be muscular in their nature, but the grounds for that admission are 
not mentioned. Mr. Bowman’s Lectures on the Eye, delivered in the summer 
of 1847, and published in 1849, show us that the then state of histology in 
this country did not enable that accomplished microscopical anatomist to 
identify the fibres of the iris with other plain (unstriped) muscular tissue. At 
p- 49 he says, ‘The fibres which make up the proper substance of the iris 
are of a peculiar kind, very nearly allied to the ordinary unstriped muscle, 
but not by any means identical with it.’ He afterwards goes on to argue that, 
as we know that the organ changes its form, and as its vessels are so distributed 
that it cannot be erectile, we have no other resource than to consider its fibres 
contractile, which conclusion he supports by reference to the striped fibres in 
the iris of birds and reptiles. 
In 1848 Professor K6lliker announced to the world his grand discovery 
of the cellular constitution of all plain muscular tissue, in a full and elaborate 
paper in the Zevrtschrift fiir wissenschaftliche Zoologie At p. 54 of the first 
part of the first volume of this journal, after speaking of the arrangement of the 
* Professor K6lliker may almost be said to have been anticipated in this discovery by Mr. Wharton 
Jones. Through the kindness of that gentleman, I have now before me two original drawings, made 
by him about the year 1843, of plain muscular tissue from the small intestine. In one of these the 
muscular fibre-cells are characteristically shown, except that their nuclei are not apparent; one of 
them is wholly isolated. In the other drawing, the alternate disposition of the fibre-cells is seen after 
the addition of acetic acid. He also observed, as he informs me, that the unstriped muscle of the oeso- 
phagus and stomach, and also of the uterus and other organs, consisted of similar elements—a fact 
which he yearly communicated to his class in his public lectures at Charing Cross Hospital. He was 
led, from appearances in the embryo, to infer that striped muscular fibre is originally composed of 
similar elements, which, in the process of development, are enclosed in a sarcolemma common to many 
of them, and become split into fibrillae. He thus accounted for the nuclei of striped muscular fibre, 
which, according to this view, are the persistent nuclei of the primitive muscular fibre-cells.—J. L. 
LISTER I B 
