New Problems in the Functional Activity of the Pacinian Corpuscle

During the last decade, investigations into the mode of function of the Pacinian corpuscle have been focussed almOst exclusively on recording the activity of its nervous components, and some of the more recent histological studies (Quilliam and Sato, 1955; Pease and Quilliam, 1957) have contributed to interpreting the results so obtained. Lately, interesting structural modifications have come to light in end-organs of the Pacinian type found in various sites in different species. Thus, the presence of a system of intracorpuscular cap-illaries draining into nearby extracorpuscular glo-merular arteri0venous anastomoses has been reported in human digital material (Cauna and Mannan, 1958), and the hitherto unsuspectedly complex morphology of the inner core of cat's mesenteric corpusdes has also been demonstrated by Pease and Qullliam (1957). These findings, together with the results obtained from employing micromechanical methods (Hubbard, 1956; Loewenstein and Rathkamp, 1958), now emphasise the desirability of considering the role played by the various non-nervous dements of this type of sense organ in its task of monitoring seemingly different processes taking place in diverse situations. The outstanding feature characteristic of all Pacinian type corpuscles is their lamellated structure , and recently Hubbard (1958) has shown that the lamellae of the outer zone of the cat's mesen-teric corpuscle (together with the fluid-filled spaces which intervene between them) act as a mechanical high pass filter, in that they effectively insulate the inner core and the nerve terminal within it from all the heterogeneous environmental stimuli, save those possessing high frequency components. The importance of this finding is that it is now unnecessary to ascribe the receptor's well known characteristic of quick adaptation to a maintained pressure stimulus solely to an inherent property of the nerve terminal itself. It also follows that, dur-Lug effective stimulation, a radially directed force is momentarily applied to the inner core. As the nerve terminal is bare both of myelin and Schwann cell sheaths (Pease and Quilliam, 1957), this force might conceivably distort its surface membrane. The possibility that such a deformation may be involved in the production of a receptor potential * has, together with other theories, already been briefly discussed by Gray (1956), but the part played by the complex inner core in channdling or otherwise modifying the circumferentially applied force is as yet obscure. Another interesting prohlem requiring clarification emerges from the realization that the distribution of both true and pseudocholinesterase in cat's pancreatic corpuscles 1956) is restricted …