"On the bands in the recti muscles"

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PDF from photocopy; Taubman Medical Library, University of Michigan.

[The PDF includes J. C. C.'s submission of comments from Mr. Mayo about Snow's January letter on recti muscles, in LMG 23 (2 February 1839): 640-41; Edward Lonsdale's response to J. C. C. and Mayo in LMG 23 (9 February 1839): 718-19; and Snow's letter transcribed below.]

To the Editor of the Medical Gazette

Sir,

You will greatly oblige me by allowing a place in your valuable journal to the following observations on the letter of J.C.C., in the Medical Gazette of Saturday last, containing Mr. Mayo's judgment on the subject of my communication in your number for the 12th inst. viz. the action of the recti muscles of the abdomen.--I remain, sir,

Your obedient servant,

John Snow.

54, Frith Street, Soho

Jan. 28, 1839.

Mr. Mayo gives us two uses for the tendinous intersection of the rectus abdominis: first, "that in certain positions of the body the recti describe a curve, and have to maintain or increase that curve while they are in action." The only action a muscle has, is to shorten itself, and in doing so, whilst it is attached at both ends, so far from maintaining or increasing a curve, its tendency evidently must be to become straight; and unless the rectus were retained in the curved form by other muscles, it could never act either on the thorax or pelvis, except when straight. After shewing that this curved form does occur, it is stated that these tendinous intersections "when braced tight by the fibres of the internal oblique, with the tendon of which they cohere, allow the intervening portions to describe arcs of segments of the entire curve, and permit the whole to become concave forwards, while its several parts are shortening, and perhaps straightening." This does not explain the use of those tendinous intersections, for the tendon of the internal oblique, together with those of the external oblique and the transversalis forms a sheath for the rectus, one half of which passes in front of it, and thus when those muscles are in action they not merely permit the whole," but they compel the whole "to become concave forwards," and would do this just as effectually without these intersections as with them.

If it were necessary to add analogical inference to direct proof, I might remark that there are many muscles without tendinous intersections which act whilst they are curved, as the muscles of the spine occasionally, and the transversus abdominis and diaphragm at all times, and that these intersections exist in the rectus of animals in which the muscle never forms a curve towards the viscera.

The other use we are given for these tendinous intersections is, that they enable one portion in length of the muscle to act occasionally without the other. Now since many of the fibres dip behind each intersection, and are continued to another one, so that no intersection divides the whole of the muscle, it is impossible to conceive how one part of the muscle can act without the rest. Mr. Mayo gives us an instance of this particular action, the gymnastic feat of raising the body by the hands, and states that the upper halves of the recti pull "the lower part of the body upwards, as if they drew upon so many belts, which are fixed and girded by the action of the oblique and transverse. The lower [719/720] halves of the recti are at the same time in moderate action." Surely the muscles would raise the lower part of the body more effectually and comfortably by drawing upon the pubes than upon these belts, and I have examined the recti of a man during this feat, and found them as hard as a board throughout their whole length. However, this action is not exerted for the purpose of pulling up the lower part of the body; this is in the same piece with the upper part, and needs no such pulling upwards, and any action between the chest and lower part of the body would no more lessen the weight to be raised by the arms and shoulders, than a person standing in a balance would lessen his weight by lifting up one leg, or pulling at the cord of the scale, or any other maneuver. This action of the recti, in addition to assisting to steady the chest, a measure necessary in all powerful actions of the arms, is exerted to draw the lower part of the body forwards, and make it project beyond the pole, to balance the upper part which is on the other side, and keep the certain gravity of the body on the same perpendicular plane with the pole, that the arms may simply have to raise the weight of the body, without the disadvantage of its being at the further end of a lever; the necessity of which is seen by the impossibility of raising the body without allowing the legs to project under the horizontal pole, or of pulling it up the side of a wall, without touching the wall with the legs or feet.

So far, then, I am fully borne out in repeating the remark with which I closed my last letter, not "denying any use in the arrangement," as J.C.C. states, but saying that "I do not think these tendinous bands execute any important office."

These bands exist, I believe, in the rectus of all animals down to reptiles. Carus says that the frog is without the transverse tendinous ligaments belonging to fishes and salamanders, and the only vestiges of them are in the recti muscles of the abdomen. These transverse tendinous bands in fishes, it should be remembered, correspond in number to the vertebrae, and the bands in the rectus of man are never more numerous than the vertebrae between the chest and pelvis, viz. five.