The author tried to study histological sections made from 563 eyes of 277 leprous rat which were caught in the city of Kumamoto and obtained the following results.
1) Morbid changes were found in 56 (10, 4%) among 536 eyes. They were almost infiltrations of the lids, and spread continuously from leprous infiltrations in the surrounding area of the lids. Then the infiltrations gradually encroached on the palpebral conjunctiva and the inside of the conjunctival fold. Further in front the infiltrations reached under the orbicular conjunctiva or to the limbus of the cornea. In the back it spread through the connective tissues surrounding the eyeball and an infiltration focus was formed around the optic nerve. At the lachrymal gland a moderate leprous affection was observed.
Leprous affections of the eyeballs were very few in number (only in 7 eyes, namely 1, 3%). The affections were found frequently in the orbicular conjunctiva and this part seemed to be the first place of changes of the eyeballs in eases of rat leprosy. And these leprous affections of the eyeballs seemed to spreadefrom infiltrated harts of the surrounding palpebral conjunctiva, slice many of them were connected with the affection of the conjunctival fold.
Leprous affection of the cornea was very few in number (only in 6 eyes, namely 1, 0%). Through every case had a moderate infiltration of cells under the limbus of the conjunctiva, only a few lepra cells wandered into the crevises of the corneal stratum. There were found no isolated lepra bacilli which invaded along lymph spaces of the cornea, as in cases of human leprosy.
Only in one case of rat leprosy a true leprous infliration and lepra bacilli were found at the middle part of the cornea far apart from the limbus. In this hart a relative intensive new growth of blood vessels and rare bacilli were demonstrable. Rare leprous bacilli were found also in the superficial layer of the limbus of the sclera, and entered from the infiltrated focus of the conjunctiva. They decreasecl in number gradually backwards and finally disappeared in the back part.
Only in one case a few lepra cells were seen near the Schlemm's canal of the deep layer of the sclera. Perhaps they came from the infiltrated focus of the orbicular conjunctiva and the external part of the sclera. These facts seemed to suggest the way of infection to the eyes in cases of rat leprosy.
No leprous affection was seen in the inside of the eyeball.
2) There were comparatively intensive non-leprous infiltrations in the palpebral glands, conjunctiva and cornea of wild leprous rat.
An another noticable change was the shrink of the eyeballs, whichl was found in 18 eyes (3, 3%) among of those of all rats examined. But no indisputable evidence of the blindness owing to leprous changes was noticed.
3) A moderate falling of the hair was observed in 93 cases (33, 6%) among all cases of rat leprosy. But they were not always combined with the leprous infiltrations of the subcutis. Accordingly there were a few cases in which leprous affections were seen in the eyes. Leprous changes of the eyes were found in a majority of rats, in which lepra baeilli were demonstrated in their subeutis and viscera.
4) Generally speaking the differences of histological findings between rat and human leprosy. i) In the tissues the bacilli of rat leprosy were sunder than that of human leprosy, and they existed almost in the cells and rarely showed cigar like-bundles. ii) Vacuoles were scareely found in the lepra cells, iii) It was comparatively rare that lepra bacilli entered into the wall of the blood vessels. iv) Affections of the nerves were very few in rats comparing with human leprosy. v) Leprous tissues of rats might become gangrenous. vi) The bacilli of rat leprosy invaded mostly themusele layers.
5) The changes of the eyes of rat leprosy, as compared with, those of human leprosy, were very slight, so that there could be no comparison between them.
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