1()>2 ON THE APPARENT FIGURK OF STARS. 



The author as- Having no human eyes at my disposal, I requested Dr. Chaus- 



sisted by Dr. gigj., professor at the School of Physic, to assist me with the 

 Chaussier, ■' 



means of ascertaining, whether the curve of the human crys- 

 talline, seen in front, was constantly a circle, as is commonly 

 supposed. This gentleman complied with my wishes j and 

 had the goodness, not only to procure me the eyes necessary 

 for my researches, but to assist me with his skill and advice. 

 , Mr R'bes ^'^^'' ^'^^^> ^^ ^^^^ time assistant dissector to the school, 

 brought us eyes of foetuses, adults, and old men. To these 

 we added eyes of sheep and oxen*, in order to compare their 

 dimensions. 

 Mode of per- ^^- ^'^^ opened some of the eyes, ^cutting thera trans- 

 forming- the versely ; and took out the crystallines with sufficient caution, 

 experiments, ^^ ascertain the place that each part occupied in the eye. Dr. 

 Chaussier likewise opened some eyes by the operation for the 

 cataract. He took out the crystallines, retaining precise marks 

 of their situation. These crystallines laid flat had all an oval 

 form. I measured with a pair of compasses the vertical dia- 

 meter CD, and the horizontal AB, fig. 15, and constantly found 

 the former greater than the latter. 

 Thecrystalline "^^^ crystalline is a kind of oblate spheroid. I call the hori- 

 described. zontal diameter, fig. 15, the length AB, which is in the direc- 

 tion of the eye-lids ; the vertical diameter, the height CD, 

 which is perpendicular to it j and the less diameter, the thick- 

 ness EF of the two segments. 



After each operation. Dr. Chaussier dipped the crystallines 



in sulphuric acid, diluted with water, in order to harden them, 



and free them from the membrane that envelopes chem. After 



Measured a- this we measured them anew ; and constantly found, that the 



^^'mbraue was ^^^""^^ °^ intersection between the two segments was elongated 



removed. in the direction of its height. 



Dimensions of In the two crystallines of a foetus the vertical diameter CD 

 the crystallines ^^g g ^^ji [3147/.], and the horizontal AB 775m. [3 04q/.]. 

 The vertical diameter of one of the crystallines of an adult was 

 11 m. [4-328/.], and the horizontal 1025 m. [4033/.]. The 

 second was not measured, because in taking it out the position 

 of each part in the eye was forgotten to be marked. The two 



• It appears from what follows, that they were the eyes of one foetus, 

 two adults, one old man, one sheep, and one ox only. 



• crystallin* 



