330 On the Mahan'ijm of the Eye, 



qdjuced for it? fupport. Lobe, or rather Albinus*, decidedly favours a fimilar theory ; 

 and fuggerts the analogy of the lens to the mufcular parts of pellucid animals, in which 

 even the beft mlcrofcopes can difcover no ISbres. Camper alfo mentions the hypothecs 

 \jrith confiderable approbation +. Profeflbr Reil publiflied, in 1793, a Diffcrtation on the 

 3trufture of the Lens ; and, in a fubfequent paper, annexed to the traiiflation of my for- 

 noer Eflay in Profeflbr^ Greo's Journal J, he difcuffed the queftion of its mufcularity. I 

 regret that I have not now an opportunity of referring to this publication; but I do not 

 recolle£l that Profeflbr Reil's obje£lions are diflerent from thofe which I have already 

 noticed. 



Confidering the fympathy of the cryftalline lens with th^ uvea, and the delicate nature 

 oi the change of its figure, there is little reafon to expe6l that any artificial ftimulus would 

 he more fuccefsful in exciting a contractive aftion in the lens, than it has hitherto been in 

 t-he uvea ; much lefs would that contraftion be vifible without art. Soon after Mr. Hunter's 

 death, I purfued the experiment which he had fuggefted, for afcertaining how far fuch a 

 conrradion might be obfervablc. My apparatus (Plate XV. Fig. 27-) was executed by Mr. 

 Jones. It confifted of a wooden veflel blacked within, which was to be filled with cool, 

 ai]^4.^cn \yitb warmer water: a plane fpeculum was placed under it; a perforation in the 

 bottom was filled with a plate of glafs ; proper rings were fixed for the reception of the 

 lens, or of the whole eye, and alfo wires for tranfmitting eledlricity : above thefe, a piece 

 of ground and painted glafs, for receiving the image, was fupported by a bracket, which 

 m©y?d by a pivot, in conne£lion witl^ a fcale divided intg fiftietiis of an inch. With tliis 

 apparatus I made fome experiments, afiifted by Mr. Wilkinfon, whofe refitlence was near 

 a flaughter-houfe : but we coujd obtain, by this method, no fatisfaftory evidence of the 

 change; nor was our expedlation much difappoinced. I underftand alio, that another 

 member of this Society was equally unfuccefsful, in attempting to produce a confpicuoua 

 change in the lens by eledlricity. 



XI. In man and in the molt com(non quadrupeds, the ftruflure of tlie lens is nearly 

 fimjlar. The number of radiations is- of little confequence ; but I find that in tiie human 

 cryftalline there are ten on each, fide, tPlatd XV. Fig. 46.) not three, as I once, from a hafty 

 cbfervation, concluded §. Thofe who find any difficulty in difcovering the fibres, mud 

 h^ve a fight very ill adapted to microfcopical refearches. I have laboured with the moft 

 obftinate perfeverance to trace nerves into the lens, and I have fometimes imagined that 

 I had fueceeded ; but I, (jjnnpt gofitlvely go further than to ftate my full conviction of their 

 e:(iflence, and of the precipitancy of thofe who have abfolutely denied it. The long nerves, 

 which are very confpicuous between the choroid and fclerotic coats, divide each into two, 



* De quibuWam Oculi Partilnis, L. B. I74G. Ap. Hall. Difp. Anat. IV. p. 301. , 



+ De Oculo Humane. L.B. 1742. Ap. Hall. Diip.' Anat. VII. 2. p. lOS, 109. 



J 1794. p. 352, 354. • 



% De Qorp. Hum.'Vir. Conf. p. f9, 



three, 



