480 Miscellaneous. 



surface of tlie limiting membrane. This has also been ascertained 

 by Miiller to be the case with animals. These fibres, which are all 

 in relation with the nucleiform botUes, of which, as already pointed 

 out by Bowman, there are two layers in the human retina, form a 

 peculiar system of the retina, and are named by us the radiating 

 fibres. The principal facts which we have ascertained respectuig 

 these fibres, which have hitherto remained unknown, are as follows : 

 every cone at its inner portion is in connexion with an enlarged body 

 containing a nucleus, which is situated in the outer layer of nuclei- 

 form bodies ; and from this enlarged body, which may be regarded 

 as a cell, a fibre arises, which attains the inner layer of the nucleiform 

 bodies and there becomes connected with one of these, which are only 

 small cells containing a large nucleus ; this fibre then traverses the 

 nervous cells and fibres, and at length attaches itself by its extremity, 

 which is inflated and sometimes ramified, to the limiting membrane. 



Radiating fibres, exactly resembling these, but finer, also rise from 

 the inner portion of the cylinders, become connected with those 

 nucleiform bodies in the two layers which are not fixed to the fibres 

 proceeding from the cones, and terminate in the same manner at the 

 limiting membrane ; it is to be observed, however, that from three to 

 six of the fibres proceeding from the cylinders unite during their 

 passage through the inner layers of the retina so as to form a single 

 fibre, which renders the radiating fibres less numerous in the inner 

 layers. These radiating fibres, like the nervous fibres of the retina, 

 are very delicate, but they never form varicosities, and may thus be 

 distinguished from the true nervous fibres. 



Such are the principal facts which we have ascertained vdth respect 

 to the anatomy of the human retina, and from these physiology may 

 derive certain conclusions of indubitable interest. We establish, in 

 the first place, that it is not by the nervous fibres of the retina that 

 light is perceived, because, on the one hand, that part of the retina 

 which is most sensible to light and which offers the most perfect 

 visual perception, the macula lutea, does not exhibit the least trace 

 of the layer of nervous fibres, whilst, on the other hand, the nervous 

 fibres exist in great number at that point where the retina is totally de- 

 ficient in sensibility. This settled, there only remain the nervous cells 

 of the retina, the nucleiform bodies, and the cones and cylinders, which 

 can be considered as organs of sensation. For our own parts, we should 

 be inclined to regard the nervous cells as fulfilling this function, as 

 it has been shown, both by Corti and ourselves, that the nervous 

 fibres of the optic nerve are continuous with these cells ; we are, 

 nevertheless, compelled to lay aside this supposition, as in all parts 

 of the retina which possess the faculty of perception, these cells form 

 several series (ten or twelve) laid one upon another, and it is impos- 

 sible to admit that we could receive exact and distinct visual impres- 

 sions, if each ray of light influenced at once ten or twelve cells. The 

 same reason leads us to think that it is not by means of the nuclei- 

 form bodies that we receive the impression of light, so that only the 

 cones and cylinders remain for our purpose. We are led to form the 

 opinion that these curious organs, with which physiology has hitherto 



