4 OBSERVATIONS ON THE 
exhibited something of a longitudinal arrangement of the granules, such as 
was noticed some years since in unstriped muscle by Mr. Bowman, who con- 
sidered the rows of granules as an approach to the fibrillae of striped muscle. 
These cells are more granular than I have found those of the iris of the horse to 
be ; but I may here mention that, on comparing with these drawings the out- 
line of a fine specimen of a muscular fibre-cell of the sphincter pupillae of this 
animal, which I had sketched by the camera lucida, I find it to be almost an 
exact counterpart of the cell (7) as regards the shape and size of both the cell 
and its nucleus. The nuclei of these cells measure from 1-1400th to 1-111oth 
of an inch in length, and about 1-g500th of an inch in breadth. They are not, 
however, the most characteristic that are to be found in the iris. Fig. 12 is 
from a camera-lucida sketch of a nucleus of the sphincter pupillae of a horse ; 
it measures 1-84oth by 1-15200th of an inch, and exhibits in a very marked 
manner the true rod-shaped figure which appears peculiar to muscular fibre- 
cells. On the other hand, I found some instances in the human iris of fibre-cells 
with considerably broader nuclei than those in the figures. The iris that yielded 
these cells was a blue one, apparently perfectly healthy ; it was active and 
brilliant before the operation, which was performed on account of central opacity 
of the cornea, resulting from an attack of a severe form of ophthalmia fifteen 
months previously. I watched the case closely from the first, and there was 
no reason to suspect implication of the iris in the inflammation. 
Having thus satisfactorily verified the fact of the existence in the iris 
of tissue identical with ordinary unstriped muscle, I was naturally led to inquire 
into its distribution in the organ: and, as this is a subject of great interest, 
and one about which much difference of opinion has prevailed, I may mention 
here the facts which I have hitherto observed, although there be not very much 
of actual novelty in them. 
Kolhker, in the article above referred to (loc. cit., pp. 53 and 54), describes 
a sphincter and dilator pupillae, the former ‘ very readily seen in the white 
rabbit, or the blue iris of a man, from which the uvea has been removed, about 
a quarter of a line broad in man, exactly forming the pupillary margin, and 
situated somewhat nearer the posterior surface of the iris’. Of the dilator 
he says, while confessing the difficulty of the investigation, that he believes 
it to consist of many narrow bundles, which run inwards separately between 
the vessels, and are inserted into the border of the sphincter. 
Bowman, on the other hand, states (op. cit., p. 48) that, while in some 
instances a delicate narrow band of circular fibres exists at the very verge of 
the pupil, yet, in the majority of instances, he feels swve that no such constrictor 
fibres of the pupil exist. He ascribes the contraction of the pupil to the inner 
