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The distal portion of the flexor muscles powering tailspine movement in the horseshoe crab is innervated by separate sensory and motor nerves. Records from the sensory nerve of an undisturbed preparation show tonic afferent activity which is increased by movement of the tailspine. Splitting the nerve, which randomly isolated small bundles of fibers, permitted identification of individual sensory units. Imposed lengthening or shortening of the passive muscle elicited unidirectional 'movement' fibers. Another class of units fired only upon active contraction and showed increased activity with increasing muscle length. These units appear to be series tension receptors. Each of the receptor types observed showed phasic and tonic activity. Reflex motor activity could be elicited by stimulation of the sensory nerve, although the identity of the afferents eliciting this activity was not determined. Methylene blue staining showed multipolar and bipolar neurons near the muscle insertions, suggesting that these might be the receptors responsible for the observed sensory activity. [ABSTRACT FROM AUTHOR]

Phonocardiography is of great importance in distinguishing coronary artery fistula from other anomalies with a continuous murmur. The presence of this murmur at the apex must be regarded as an important characteristic of a coronary artery fistula, especially when the maximum diastolic murmur is found at the apex. Although coronary artery fistula may be symptomless for a long time, surgical treatment is desirable in most cases. Extracorporeal circulation should be used in all operations for coronary artery fistula to avoid ligation of the wrong artery or failure to close all fistula orifices. [ABSTRACT FROM PUBLISHER]

An evolutionary scheme is postulated in which the bases enter the genetic code in a definite temporal sequence and the correlated amino acids are assigned definite functions in the evolving system. The scheme requires a singlet code (guanine coding for glycine) evolving into a doublet code (guanine-cytosine doublet coding for gly (GG), ala (GC), arg (CG), pro (CC). The doublet code evolves into a triplet code. Polymerization of nucleotides is thought to have been by block polymerization rather than by a template mechanism. The proteins formed at first were simple structural peptides. No direct nucleotide-amino acid stereo-chemical interaction was required. Rather an adaptor-type indirect mechanism is thought to have been functioning since the origin.