Traumatism and infection play a part probably in all forms of ulcerative kera titis. Germs are always present in the conjunctiva and atmosphere. So that in the absence of resisting power on the part of the tissues every wound becomes infected. When, however, the germs are markedly pathogenic, as in the conjunc tivitis which attends chronic lacrymal obstruction, or in that due to acute in fection of the conjunctiva, the corneal lesion proves more serious. Swelling of the conjunctiva around the corneal mar gin, ehemosis, prevents the lids from cleansing the cornea, produces a sulcus, in which the infected discharges tend to accumulate. It is in this way that chemosis causes corneal involvement in gonorrhceal conjunctivitis. The pecul iar forms of different ulcers and the way they extend are largely dependent on peculiarities in the growth of the or ganisms that cause them. Thus, the ser pent ulcer, with its rapid extension later ally and its abrupt or overhanging mar gin, is probably due to the growth of the pneumoeoccus, which tends to spread be tw-een the layers of the cornea without penetrating them. Dendritic ulcer is probably also due to infection. Ilullous Iseratit.s inav arise from obstruction in the 1% niplt-(liannels in the part. Patintis is due to traumatisms by the roughened Is, probably with an added specific irri tant. Nerotie keratitis may be infective, althoug,11 the so-called xerosis bacillus is found abundantly in the normal con junctiva.
Summary given of 130 cases of keratitis interstitialis diffusa, including 5 cases of keratitis interstitialis annularis. In the 5 cases of the annular form of the disease 4 were over 20 years of age. Its etiology remains unexplained. In 125 eases of the diffuse form hereditary syphilis could be positively determined in only 40 in stances. Pfister (Cursalon Zeit. f. Bal neol., :Mar., '90).
Among 15,000 patients only 42 cases of interstitial keratitis were found; of this number 16 were males and 26 females. As a rule, the affection was bilateral, in only 9 eases occurring on one side. The average age of development was I31/2 years, the earliest being 3 months and the latest 30 years. The complications of most frequent occurrence were affections of the traetus uvealis, and especially iritis; in all, characteristic teeth were found in 40 per cent. In more than half the cases hereditary syphilis could be proved (55 per cent.). Werndly ("Kera titis Diffusa," '91).
Two cases of keratitis, 1 of them com plicated ith iritis, occurring in women of advancing age suffering from malig nant uterine disease. The ocular trouble believed to have been caused by infec tious emboli. Du Bois-Reymond (Zehen der's klin..Monats. f. Augenh., Apr., '91).
Case of periodically-occurring attacks of keratitis, apparently depending upon menstrual disorder and chIorosis. Usu
ally both eyes were affected, the attacks beginning after the appearance of the flow and lasting a few days longer. In the intervals the eyes were well and the vision good. Ransohoff (Zehender's klin. Monats. f. Augenh., Aug., '91).
In the exudate of scrofulous keratitis was found a coccus colored by Gram's method, liquefying in gelatin and pro ducing keratitis in rabbits, which was be lieved to be staphylococcus pyog,enes. Straub (I.a Sem. MM., May 25, '92).
Clinical, anatomical, and experimental facts point to interstitial keratitis even IN hen it is clinically a primary manifesta tion, being either a symptom of an exist ing or a consequence of a previous morbid process in the uveal tract. What may be called clinically primary interstitial ken atitis appears to have no uniform eti ology. Hereditary syphilis is the most important and most frequent cause; local conditions may, however, influence the proportion in which this cause preponder ates. Against the exclusive importance of syphilis inay be mentioned:— The absence of other indications of hereditary or acquired syphilis in 30 per cent. to 50 per cent. of the eases.
The occurrence of interstitial keratitis in animals.
The anatomical demonstration that the condition may sometimes depend upon a tubercular infection of the eye.
The fact that diseases of the uveal tract may be due to various causes.
Individuals who have never acquired syphilis may suffer in advanced life from interstitial keratitis.
Hutchinson's teeth do not appear to occur in the majority of cases; their presence points to the probable, though not the certain, existence of hereditary syphilis.
Recurrences of interstitial keratitis are not uncommon. E. v. Hippel (Graefe's Archiv, xlii, 2).
Dendritic keratitis considered an her petic disease of the cornea due to con stitutional causes, malarial poisoning be ing very prominent. Wilder (Med. News, July 15, '93).
Of 25 cases of hypopyon keratitis, the diplococcus was found in 23, either alone or associated with a staphylococcus. In 4 cases the micrococcus occurred in phleg monous disease of the eye. Guaita (Recueil d'Oplital., June, '94).
In the majority of instances of hypop yon keratitis the infectious agent is the diplococcus of Friinkel. In nearly all per sonal cases the germ was found in the mouth, giving rise to the suspicion of disease in that cavity. Bassa (Recueil d'Oplital., June, '94).
Interesting case of parenchymatous clouding of the cornea following light ning-stroke in a girl 11 years old. There was present almost complete amblyopia and marked blepharospasm. After IS days the cornea cleared spontaneously, and the 'patient regained full visual acuity. Denig (Munch. med. Woch., Aug. 20, '95).