The Anatomy of the Infra-red Sense Organ in the Facial Pit of Pit Vipers

摘要: SUMMARY 1. The histological composition of the sensory membrane in facial pit rattlesnakes (Crotalus spp.), disposition nerve-trunks entering it, fibre-size spectrum nerves, and form endings are described. 2. Between two layers extremely attenuated epidermis principal constituent is a single layer specialized parenchyma cells with osmiophil, reticular cytoplasm. These not regarded as sense but they react strongly locally to degeneration nerve-endings. 3. axons enter through numerous trunks from three branches trigeminal nerve, all sides membrane, providing dense innervation. They lose their myelin, taper about 1 JJ,, then expand into flattened palmate structures which bear many branched processes terminating freely over an average area I,SOOJU. 3 , overlapping only slightly adjacent units leaving virtually no unsupplied. This means there 5 00 1,5 ending per mm 2 estimate agrees nerve-counts. No other was found. 4. mode lies region 5-7/J, diameter. 5. A transmission fresh shows broad absorption peaks at 6 /x 50% transmitted regions out 16/n. visible least probably much lost by reflection. Strong takes place wavelengths shorter than 490 /A. 6. anatomical adaptations organ discussed, especially concentration warm receptor fibres, thinness superficial position nerve-endings—all increasing sensitivity caloric flux. overhanging margins richness supply believed permit directionality reception. 7. It suggested that has significance permitting several independent local sub-threshold activity generators coexist pooling coincident, electrotonically spread potentials influence initiation spikes may take junction axon palm.