Geographical Positions of Places, Sfc, 2f8t^ 



humour, is inserted into the outer, or fibrous layer of the retina, 

 which now proceeds forwards, lined internally by a dark 

 pigment, differing in tint from that which covers the inner 

 surface of the nervous part of the retina, as far as the ciliary 

 ligament d, a little behind which, as I have said, it is joined by 

 what I am inclined to consider a rudiment of the choroid e. At 

 the ciliary ligament, this fibrous layer of the retina is reflected, 

 and passes straight across to the crystalline, between the anterior 

 and posterior hemispheres of which it extends, i. This mem- 

 brane, between the ciliary ligament and the circumference of 

 the lens, is covered posteriorly by another membrane, k, coloured 

 with a pigment, which is folded in a radiating direction, and 

 extends from the ciliary ligament to the circumference of the lens, 

 where it is continuous with the posterior concentric laminae, /, of 

 that body. Anteriorly, there is a similar membrane, m, the 

 anterior surface of which is covered by what seems to be a 

 reflection, n, of the iris. The iris, which, at the margin of the 

 pupil, e, is joined by the conjunctiva, (represented by the dotted 

 line,) is covered behind by an uvea, and is inserted into the 

 ciliary ligament, where it sends off the reflection, n, which 

 covers the anterior surface of the crystalline. The crystalline, 

 which is spherical, resembles in structure that of the higher 

 animals ; but is composed of an anterior, p, and posterior, q, 

 hemisphere, joined to each other, through the medium of the, 

 fibrous layer of the retina, which passes between them, and the'' 

 folded membranes, on its anterior and posterior surface, — parts 

 which are analogous to the ciliary processes in the higher^^' 

 animals, the anterior folded membrane corresponding to th^^^" 

 true ciliary processes, and the posterior membrane to thd 

 structure, called the zonule of Zinn. The vitreous humour is;* 

 not contained in cellules, but fJows out when the hyaloid i^' 

 punctured, or when the anterior part of the eye is destroyed. ^ 



ART. Y.— Geographical Position of the Principal Places onthci. 

 Frontiers and Interior of the Province of Buenos Ay res. By '7 

 4l6»N-GiLLiEs, M.D. Member of the Wernerian Society, &c.' 



tvi^-n - -^ -■ 



The following positions were originally published in the 

 Registro Estadistico, a periodical register brought out under the 

 auspices of the government of Buenos Ayres. This publication* 

 was commenced in February, 1822, with the view of investiga- ' 

 ting the statistics and geography of the province, and of affording ' 

 an opportunity of publishing all the most important documents/ 

 connected with this subject which were to be found in the public^ * 

 archives of Buenos Ayres. "j 



The data from which these geographical positions were laid! 

 down, were the astronomical observations made in 1796 byrf 

 Don Pedro Antonio Cervino, geographical engineer, and Don' ' 

 Juan Inciarte of the Spanish mariDe^,,,. ^^^ ^i,i^ot> ^.^j-^ 



