It is not easy to obtain a view of these exudates in section, but nevertheless they appear in a considerable number of the microscopic specimens, and their character is always the same; they consist of more or less structureless masses with blood-cells and leucocytes imbedded in their substance. In fact, they would seem to be identical with the membrane spoken of by Straub as harbouring the leucocytes which gave rise to dust-like and other opacities of the vitreous in his experimental cases. At a later stage, or perhaps in cases where the inflammation has been of a more plastic character, a distinct fibrillation of the exudate can be seen, and there may even be evidence of a definite fibrous tissue formation. If we confine our attention for the moment to those eyeballs in which the exuded mass is devoid of structure in the anterior portion of the cone, we shall find that, on tracing it back toward the apex by which it is attached to the optic nerve, it becomes more highly organised and more richly cellular, whilst fibrillation and fibrous tissue formation make their appearance. The same thing, though in a lesser degree, may be observed in the neighbourhood of the ciliary body, doubtless due to the presence of a plastic exudate derived from that structure. An examination (Pl. VI., Fig. 38) of the optic nerve and of the exudate attached to it reveals the following features: (1) The nerve head is congested, and its vessels stand out in prominent relief. (2) There is a considerable effusion of leucocytes in the neighbourhood of these vessels. (3) A mass of exudate fills up and projects from the optic nerve cup, whether this latter is physiological or glaucomatous. This mass is clearly contracting, and thereby pulling on the tissue which lines the edges of the cup. (4) Along the centre of the projecting exudate are to be seen (_a_) an abundance of mononuclear cells; (_b_) the commencement of a fibrous tissue formation; and (_c_) a new formation of bloodvessels. The appearances above enumerated would indicate that we have to do with an inflammation of the optic nerve, which had been induced by chemotaxic substances brought thither along Stilling’s canal. Such an idea is not a new one. It was suggested by Straub in order to explain the optic neuritis he found in his two cases of experimental inoculations of the ciliary body, and it also enjoys provisionally the support of Fuchs’s[3] authority. The idea that part of the lymph of the eye passes backward along a passage corresponding to the central hyaloid canal is not generally accepted, and rests largely on inference from the observation of pathological specimens. It would be difficult, however, for anyone who has carefully studied this series to doubt that such a flow exists; it is, of course, not suggested that any large percentage of the lymph travels in this direction. [3] Fuchs: “Textbook of Ophthalmology,” Duane, fourth edition. 1911, p. 16.