in Anatomy and Physiology. 263 
his views, but from our knowledge of this tissue, the phases of 
its formation from the earliest to the perfect state, and the various 
appearances it presents in different parts of the animal kingdom, 
e are led to venture the conjecture that its alleged spiral struc- 
ture, may be due to irregularities and anomalies of contraction. 
IV. On the presence of a layer of transversely striated. muscular 
fibres in the Choroidea of Birds. 
muscular fibres in the posterior portion of the choroidea of the 
certain extent by Henle; but Wittich has been unable to observe 
ra, and in man; he has, however, contrary to the statements 
of Rainey, detected this tissue in the whole posterior half of the 
choroidea of birds. As to the manipulation and preparation for 
the observation of this tissue, I will.quote Wittich’s own words: 
“For the most intimate research, I can best recommend the 
eye of the thrush. This having lain a short time in diluted alco- 
hol, not only the retina, but also its subjacent membrana pigmenti 
can be entirely removed. This being done, the choroidea can be 
p- 
arated from it. . Between this external tunic and the membrana 
wards the ciliary border, the meshes becoming more open, but 
they are most numerous towards the pecten of the choroidea. 
* Siebold & 
“ Deser 
Killiker’s Zeitsch. f. wissenschaftl. Zool. IV. p. 456, Apr. 1853. 
i a muscle of the striated variety, situated at the posterior pa 
of the choroid coat of the eye in Mammals, with an explanation of its mode of ac- 
tion in adapting the eye to distinct vision at different distances.” By Geo. Rainey, 
Roy. Soc. 1851, Jan., p. 28. eee rhe 
Rainey regards this choroid muscle as the analogue of the ciliary muscle of birds, 
& view which, Wittich shows to be unfounded. 
i: 
