LACRYMAL ORGANS. 



87 



removed and the papillary body then separated 

 by a shaving cut through the surface of the 

 conjunctiva. The papillae are seen under a 

 microscope magnifying three hundred diame- 

 ters, as yellowish red corpuscles standing close 

 together, of an arched conical shape and pre- 

 senting a round nucleus in their interior. 

 Many of the papillae have short pedicles. Many 

 present at their extremity a small point or fila- 

 mentous prolongation which runs towards the 

 epithelium. Henle* thinks Valentin's papillae 

 are nothing but the corpuscles of the epithe- 

 lium, presently to be noticed, distorted by the 

 action of the compressorium. Itappears to me 

 that Valentin's papillary body constitutes a 

 structure of the same nature as the corpus 

 Malpighianum of the skin. We know that 

 such exists in the sclerotic conjunctiva from the 

 circumstance that in negroes and many of the 

 lower animals it is tinged of a black or brown 

 colour, whilst in Isabella horses and in Swiss 

 races among oxen it appears yellowish. 



Epithelium of the conjunctiva. The dis- 

 covery of a characteristic structure in epithe- 

 lium enables us to determine its existence even 

 when so delicate as not be separable as a dis- 

 tinct layer. It may appear merely as a tena- 

 cious mucus little more than perceptible to the 

 naked eye, but examined under the microscope 

 it is found to consist of minute polygonal 

 cells, flat and containing a central nucleus. 

 These corpuscles aggregated together more or 

 less closely and in greater or less quantity con- 

 stitute the substance of epithelium. The epi- 

 dermis is essentially of the same structure ; as 

 also the corpus Malpighianum, only when this 

 is coloured, the cellules are found to contain 

 colouring particles, as is remarkably the case 

 in the black pigment of the eye, the small 

 hexagonal bodies composing the membrane of 

 which belong to the same category as the cor- 

 puscles of the epithelium or corpus Malpi- 

 ghianum. 



According to Valentin the epithelium of 

 the conjunctiva consists of rhomboidal or quad- 

 rate cells lying close together, the boundaries of 

 which are formed by simple lines. In every 

 cell there is found without exception a some- 

 what darker and more compact nucleus of a 

 round or largish form. The average diameter 

 of these cells, in the human eye, is about the 

 two-thousandth of an inch. The nuclei are 

 about half the size. 



Thickening of the epithelium takes place in 

 ectropium and callous granulations. What is 

 called cuticular conjunctiva is at the same time 

 a general contraction of the whole conjunctiva 

 with a thickened and dry state of the epi- 

 thelium. 



Does the conjunctiva extend over the cornea ? 

 Every one admits the existence of a layer on 

 the anterior surface of the cornea, quite dif- 

 ferent from its proper substance, and apparently 

 a continuation of the conjunctiva covering the 

 sclerotica, but this layer on the anterior surface 



* Symbols ad Anatomiam Villorum intestina- 

 lium, imprimis eorum epithelii et vasorum lac- 

 teorum, p. 8. 4to. Bcrolini, 1837. 



of the cornea does not present exactly the same, 

 or at least all, the anatomical and chemical 

 characters as the sclerotic conjunctiva. What 

 of it can be raised is like epidermis or epithe- 

 lium, coagulated and rendered white by the 

 heat applied to separate it, and moreover it is 

 not vascular, the vessels seen ramifying on the 

 surface of the cornea in some inflammations 

 being situated underneath it. 



What is the nature of the superficial layer of 

 the cornea ? It is composed of two lamellae. 

 The more superficial constitutes a very fine but 

 firm epithelium. According to Valentin, after 

 sixteen or twenty-four hours' maceration, the 

 epithelium separates from the cornea. The 

 cells have in this case lost a little in transpa- 

 rency and are somewhat distended. The nuclei 

 appear more or less swollen by the action of 

 the water. The other lamella situated under- 

 neath the epithelium is more loose in its co- 

 hesion, and is what Valentin considers the 

 same structure as the papillary layer described 

 by him in the ocular conjunctiva. Valentin 

 says that a chorion or fibrous layer does not 

 exist in the conjunctival extension over the 

 cornea. The bloodvessels derived from the 

 sclerotic conjunctiva run merely betwixt the 

 papillary body and the surface of the proper 

 substance of the cornea. They are very deli- 

 cate and extremely difficult to inject. 



Romer* has described the arteries of the con- 

 junctiva corneae from injections. The fine 

 twigs of the arteries of the sclerotic conjunctiva 

 unite together around the margin of the cornea 

 into a vascular wreath or circle. From this 

 there arise very numerous branches which run 

 from the circumference towards the centre of 

 the cornea, and in their course make two or 

 three very fine subdivisions. Their ends bend 

 distinctly inwards, and appear to penetrate the 

 proper substance of the cornea. 



Having thus shown on the surface of the 

 cornea the existence of an epithelium and a 

 structure, called by Valentin a papillary body, 

 similar to what is found on the surface of the 

 sclerotic conjunctiva, as also a stratum of blood- 

 vessels, we must admit a cellular support for 

 those vessels, however delicate. If so, the 

 bloodvessels and cellular tissue would consti- 

 tute the essential elements of a chorion. f We 

 can only explain the development of those ex- 

 tensions of membrane like sclerotic conjunctiva, 

 over the cornea by supposing an irregular and 

 undue development or hypertrophy of these 

 elements. 



The question, "Does the conjunctiva' ex- 

 tend over the cornea?" may be considered as 

 answered in the affirmative by the above ana- 

 tomical demonstration. Morbid anatomy 

 now comes in advantageously with its corro- 

 borative evidence. " Nothing is more in 

 favour," says Eble, " of the existence of a con- 



* In Ammon's Zeitschrift Bd. v. p. 21, Table 1, 

 Fig. 9 and 11. See also Miiller's Archiv, 1836 \ 

 Jahresbericht, p. 28 ; and Henle De Membrana 

 Pupillari, Sec. Bonnae, 1832. 



t Medico-Chimrgical Transactions, vol. xxi. p. 

 414, London, 1838; London Medical Gazette, vol. 

 xxiii. pp. 571,702, 815. 



