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Introduction
Being a 4th year medical student my interest in heart structure led me into a series of maroscopical studies of the ventricular myocardium which enable me, twenty five years later, to lay down, in a coherent and comprehensive survey, the morphological basis of myocardial function.
To make such results more accessible to any reader, I must first comment on the vocabulary generally used in morphology and on the one used in my descriptions.
When speaking about fibres and layers, we must keep in mind that, in macroscopical dissections, these morphological units are not precisely definable. As these units are dissected it only means that a myocardial mass, bigger (layer) or smaller (fibre), is arbitrarily separated from the whole. When any part of the myocardial body is manually isolated, it only has a single constant characteristic in all hearts : its preferential direction, that I call linear pathway or trajectory, when referring to fibre, or laminar pathway or trajectory, when referring to layer.
That muscular pathways or trajectories, linear and laminar, usually identified as sliding planes (plans de clivage or planos de deslizamiento), are infinite since their size, and morphological characteristics, depends on the dimensions of the muscular mass selected by dissection. It is, therefore, not possible to define or to isolate identical fibres or layers in two hearts. In blunt dissections only the preferential pathway, linear trajectory or laminar trajectory, is constant at any site in the ventricular wall. That is why it can be said that the myocardial unit has a functional identity rather than a morphological one since the function of any muscle (contractile linkage between two points) depends on the direction of its longitudinal axis, i.e., on the disposition in the space of its preferential pathway, of its trajectory.
Finally a semantic question ; in anatomy the word
"apical" means "up" or cranial. It is, therefore, not correct to use
"apical" in relation to the apex of the heart ; the term apexian would be more
logical. But, nevertheless, in the present paper I will use such terms, those of fibre and
layer and the word apical because they have been hollowed by usage and understood by all.
In this study about 1000 hearts, including those of man, horse, ox, sheep, dog, pig, cat, hen, turtle, lizzard, fish and the circulatory system of worms, have been disected.
The hearts were prepared by boiling them in water to become soft the connective tissue. The period of boiling was judged empirically on the appearance of fibres and depended on the size of the specimen ; 10 minutes or less for a hen heart and up to two hours for an adult ox heart.
After boiling, the atria, aorta and pulmonari artery were removed from the heart. The fat of the atrio-ventricular sulcus was separated and all the superficial coronary vessels excised.
Dissection of the myocardial mass was undertaken with non-toothed forceps, scalpel and scissors. Blunt dissection with the fingers was generally the most satisfactory way of identifying the direction of the linear (fibre) and laminar (layer) pathways.
Gentle longitudinal traction was enough to separate long strips of myocardium whereas forcible lateral traction tended to tear the muscle fibre.