Experimentally-induced petechial hemorrhage and white embolization in the rabbit's nictitating membrane☆

Abstract 1. 1. Various hemorrhagic agents were injected intradermally into ear, abdomen, conjunctiva, and nictitating membrane of about three hundred nonanesthetized male rabbits, and biomicroscopic observations were made at the site of injection. 2. 2. Different areas of the skin of the same animal differed in the degree of petechial production with the same test agent. Because of this finding these regions were not considered conducive to any approach of a quantitative nature. The best region found for observational studies of petechial hemorrhage was the nictitating membrane. 3. 3. A new technique which utilizes both nictitating membranes of the rabbit's eyes was developed and is described to test the fragility of the minute blood vessels within a three-hour test period by the time of occurrence and number of petechiae. 4. 4. At a given dosage administered, a correlation was found between the number and the time of occurrence of petechiae. When different dosages were used, the number produced correlated directly with the dosage. Physiologic saline, distilled water, and mineral oil served as controls and did not produce petechiae. 5. 5. It was possible to divide the animals into two groups, those susceptible and those resistant to induced hemorrhage by a given test agent. 6. 6. Individual variations were found in the reparability of the damaged vessels. Some animals repaired these vessels in a few hours, while others required days. 7. 7. The following agents were used locally to produce petechial hemorrhage in the nictitating membrane: Merthiolate, Shiga protein toxin, moccasin snake venom, croton oil in mineral oil, sodium heparin, heparin plasma, saline plasma, citrate plasma, serum, clostridium welchii toxin, clostridium septicum toxin, streptolysin streptococcus pyogenes Group A, cysteine hydrochloride, and tricresol. 8. 8. Capillary ruptures induced by croton oil are probably due to the formation of large particles which embolize. The embolization of these vessels leads to their rupture and petechial manifestation. 9. 9. The local or systemic injection of heparin results in the constant occurence of white emboli in the nictitating membrane. It appeared that these emboli were of a different nature than those produced by croton oil. 10. 10. The local injection of heparin always resulted in petechiae in the nictitating membrane, although the systemic injection of heparin alone did not necessarily result in petechiae. Systemic heparinization combined with Merthiolate always produced petechiae in the nictitating membrane. 11. 11. When local application of Merthiolate or croton oil was preceded by the systemic injection of sodium heparin, more petechial hemorrhages resulted. 12. 12. The first occurrence of white emboli preceded or was observed simultaneously with the first occurrence of petechiae. Such emboli were not, or only rarely, observed following injections of moccasin snake venom and Merthiolate into the nictitating membrane, although innumerable petechiae occurred with these agents. 13. 13. Serum, heparin plasma, and citrate plasma, from rabbit origin, produced white emboli and petechiae following local injection in the nictitating membrane. With the exception of citrate plasma, petechiae were always produced. The latter appeared to diminish petechial formation and also the appearance of white emboli, both of which were lacking in the nictitating membrane of one animal but present in the four membranes of two other animals.