| Abstract: | Summary 1. A high percentage of frog sera (ofRana esculenta andRana fusca) reacts positively with respect to many pathogenic and apathogenic leptospira-strains; this reaction is highest (100%) with respect to the incomplete biotype ofL. icterohaemorrhagiae.2. Under natural conditions frogs do not excrete leptospirae with the urine and neither is this the case, when a single leptospira has somehow succeeded in penetrating into them. This penetration does not easily take place.3. By the inoculation of many virulent leptospirae it is possible to break the congenital immunity. Up till 3 days after the inoculation leptospirae can be detected in the blood, up till 7 days in the liver and kidneys. The frogs did not appear to fall ill.4. Frogs do not play a part in the epidemiology of Weil's disease.5. In normal frog sera precipitation of the agglutinins by means of ammonium sulphate and acetone alcohol could not be observed so definitely as in immune sera. Normal frog serum is thermostabile at 56–57°C., immune serum thermolabile at the same temperature. These differences are explained, in accordance withBordet, by the lesser strength of the antibodies in normal sera. |
