ABDOMEN. 



17 



of the muscles is provided against by the 

 variation of direction in the fibres of the several 

 layers ; thus the fibres of the obliqui are in 

 the directions of two intersecting diagonals, 

 and those of the transversalis are different from 

 both. By this arrangement a sort of network 

 is formed, with meshes so small as to render 

 a protrusion perfectly impossible in the healthy 

 condition of the muscle. In the compression 

 of the viscera the abdominal muscles are most 

 completely congeneres, although the trans- 

 versalis seems to be the best adapted to this 

 action, and probably, for that reason, forms 

 the layer which is placed nearest the peri- 

 toneum. The recti muscles are powerful 

 auxiliaries in affording a fixed point of attach- 

 ment in front for the aponeuroses of the broad 

 muscles, and the pyramidales assist in a 

 similar manner by rendering tense the linea 

 alba. Is this constant action of the abdominal 

 parietes on the viscera necessary or favourable 

 to the due performance of the functions of 

 those organs, or to the continuance of the 

 abdominal circulation? There certainly does 

 not appear to be any evidence for the necessity 

 of them for this purpose : that they are favour- 

 able to it may be inferred from the fact that 

 they do bear their present relation to them. We 

 know from numerous experiments on animals, 

 that both the transmission of the intestinal 

 contents, and the abdominal circulation may 

 go on when the abdominal muscles have been 

 freely opened or removed. Hence we may 

 answer this question with perfect justice in 

 the words of Bichat : " The walls of the ab- 

 domen favour these functions by their motions; 

 but these motions are by no means essential 

 to them." 



It is in consequence of the power which the 

 abdominal muscles thus appear to exert in 

 compressing the viscera, that some physiolo- 

 gists have attributed the act of vomiting to their 

 action united with that of the diaphragm; and 

 Magendie, reviving the opinions of Bayle, Chi- 

 rac, and Shwartz,* went so far as to deny to 

 the muscular coat of the stomach any partici- 

 pation in this act, and to ascribe it wholly to 

 the influence of the abdominal muscles. But 

 Beclard, to whom the question was referred by 

 the Academy of Medicine of Paris, proved 

 satisfactorily that the abdominal muscles are 

 active in producing vomiting when the sto- 

 mach is distended in a certain degree, and that 

 the muscular coat of the stomach is also active 

 in emptying the contents of that viscus. This 

 conclusion Ilaller had arrived at long ago, and 

 clearly expresses it in the following passage : 

 " Evidentissimum ergo videtur, vomitus qui- 

 dem causam esse in ventriculo eumque in con- 

 tractionem niti propriis viribus atque aliquando 

 vomitum perficere. Plerumque tamen irrita- 

 tionem in ventriculo natam et sensum summae 

 anxietatis, quae vomitum praecedunt, facere ut 

 ad levandam acgrimoniam vires diaphragmatis 

 et musculorum abdominis excitatce atque mo- 

 lestiam de homine amoliturae, vomitum per- 



* Vide Haller, Elemenla Physiologiae, t. vi. 

 sect. iv. xiv. 

 VOL. I. 



ficiant. Unde neque a sola vokmtate in pie- 

 risque certe mortalibus vomitus cieri potest 

 neque a sola absque voluntate natura Quare 

 recte conjunctas vires ventriculi et or^anorum 

 respirationis Cl. Viri fecerunt. Et videtur dia- 

 phragma et abdomen plus viriuin habere,quando 

 ventriculus aut cibis repletus est, aut clausis 

 ostiis distentus : tune enim magis ad perpen- 

 diculum proximum ventriculum comprimui.t ct 

 tota contingunt."* 



If it be admitted that the abdominal muscles 

 are active in producing vomiting, and in defe- 

 cation and micturition, it will follow likewise 

 that they must assist in parturition. While* 

 these pages were preparing for press, the fol- 

 lowing passage presented itself to me, in an 

 able and interesting review of M. Velpeau's 

 Treatise on Midwifery. It so fully illustrates 

 the part which the abdominal muscles take in 

 promoting parturition, that I venture to tran- 

 scribe it, " It is certain," says the reviewer, 

 " that a woman who ' bears down ' as it is 

 termed, with all her force, who makes the most 

 of her pains, however feeble they may be, will 

 thus accelerate her delivery ; and that another 

 may more or less delay delivery by voluntarily 

 opposing muscular action as much as she can. 

 For example; a woman was admitted for de- 

 livery at M. Baudelocque's theatre ; labour 

 went on regularly, and the pupils assembled. 

 The dilatation of the cervix now slackened, and 

 no progress was made during the whole night. 

 The iltves were fatigued and retired ; the pains 

 immediately returned, and dilatation again 

 went on. The young men again entered ; the 

 phenomena of labour again ceased. Baude- 

 locque, suspecting the cause, gave a hint to the 

 students to retire, but to be at hand and enter 

 upon a given signal. The patient now began 

 to ' bear down,' and the head of the child was 

 quickly at the vulva The spectators were 

 once more brought to the scene of action, and 

 the labour was speedily terminated ; for it had 

 now advanced too far to be suspended by any 

 voluntary effort or moral alarm of the woman."f 

 The fixedness of the inferior attachment of 

 the abdominal muscles to the pelvis, and the 

 mobility of the ribs, to which they are attached 

 superiorly, evidently indicate that these muscles 

 are destined to act upon the thoracic cavity. 

 The transversalis does not, from the direction of 

 its fibres, admit of this action to any extent; 

 that office, therefore, devolves chiefly on the 

 obliqui and recti. When these last-named 

 muscles act together, they must compress the 

 inferior opening of the thorax, draw its inferior 

 margin downwards and backwards, and, by the 

 compression thus exerted on the abdominal vis- 

 cera, push them upwards against the diaphragm, 

 which muscle is thus made to ascend into the 

 thorax, and that cavity is thereby diminished 

 in its vertical and antero-posterior diameters, 

 and also, though not so obviously, in its trans- 

 verse. Hence the lungs become so compressed 

 as to be adapted to the altered capacity of the 



* Haller, ubi supra. See, also, Richeiand, Physi- 

 lo^ie par lierard, art. Digestion, xxiv. 

 t Medical Quarterly Review for April, 1835. p.lOO, 



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