2 OBSERVATIONS ON THE 
fibres of the ciliary muscle, the sphincter pupillae, and dilator pupillae, he makes 
the following statement: ‘The elements of all these muscles are undoubtedly 
smooth muscular fibres. In man I have but seldom succeeded in isolating 
the individual fibre-cells, but I have had more frequent success in the case of 
the sheep, where I found them in the ciliary muscle, on an average, I-600th 
of an inch in length, and 1-4000th to 1-3000th of an inch in breadth. In man, 
in all these muscles one sees, as a rule, only parallel fibres projecting to a greater 
or less extent at the edges of small fragments of the tissue, these fibres exhibiting 
in abundance the well-known elongated nuclei, either with or without the aid 
of acetic acid. In man, the muscle of the choroid (ciliary muscle) has broader 
and more granular fibres and shorter nuclei than the iris. In the former the 
nuclei measure from 1-2400th of an inch to 1-1333rd of an inch; in the latter 
as much as I-1ogoth of an inch.’ 
Here, then, we have, so far as I know, the first and only recorded observa- 
tion of tissue in the iris identical with ordinary unstriped muscle. 
It is to be remarked that, where he alludes, in the passage above quoted, 
to having in rare cases separated the individual fibre-cells of the muscular 
tissue, Professor Kolliker speaks of the three muscles (ciliaris, sphincter, and 
dilator) collectively ; in other words, that he does not tell us in plain terms 
that he has isolated the fibre-cells of the iris at all. Now, the ciliary muscle 
is confessedly easier to deal with than the iris. Mr. Bowman, who speaks 
so doubtfully of the fibres of the iris, says of the ciliary muscle, ‘ the fibres are 
seen to be loaded with roundish or oval nuclei, often precisely similar to those of 
the best marked examples of unstriped muscle’ (op. cit., p. 53). Another very 
eminent microscopical anatomist has informed me, as the result of his experi- 
ence, that it was easy to identify the tissue of the ciliary muscle with that of 
other organic muscle, but that this had not been the case with the iris. That 
Professor Kolliker’s isolation of the fibre-cells of the muscles of the eye was 
in reality confined to the ciliary muscle is rendered probable by the fact that, 
while the whole article quoted from shows a manifest desire on the part of its 
author to give al! available detail, yet regarding the iris he mentions no facts 
requiring isolation of the fibre-cells for their determination ; while, on the other 
hand, he tells us that the fibre-cells of the iris are narrower than those of the 
ciiary muscle, and gives the length of the nuclei in the human iris—things 
which are very readily observed without isolation of the fibre-cells. His figures 
refer to the human ciliary muscle alone ; and the only measurements given by 
him of muscular fibre-cells from the eye refer to the same muscle in the sheep. 
It would seem, then, that with regard to the iris, KOlliker’s prooi falls 
short of the test of isolation of the fibre-cells. 
